Endocrine

Hypogonadism in men: workup and testosterone replacement

Clinical Overview and When to Suspect Male Hypogonadism

— Primary (hypergonadotropic) hypogonadism: testicular failure → low T, high LH/FSH. Causes: Klinefelter (47,XXY), mumps orchitis, chemo/radiation, trauma, varicocele, hemochromatosis (late), cryptorchidism.

— Secondary (hypogonadotropic) hypogonadism: hypothalamic/pituitary failure → low T, low or inappropriately normal LH/FSH. Causes: opioids, glucocorticoids, obesity, OSA, hyperprolactinemia, pituitary tumor, hemochromatosis (early), Kallmann, anabolic steroid use, severe systemic illness.

— Symptoms: low libido, ED, decreased morning erections, fatigue, depressed mood, loss of body hair, gynecomastia, hot flashes, infertility, decreased muscle mass, low-trauma fracture.

— Middle-aged/older men with obesity, T2DM, metabolic syndrome, OSA, chronic opioid therapy are the dominant secondary causes encountered in primary care.

— A 35-year-old with anosmia + delayed puberty → think Kallmann (GnRH neuron migration defect).

— Tall man with small firm testes, gynecomastia, infertility → Klinefelter; check karyotype.

Definition: clinical syndrome resulting from failure of testes to produce physiologic testosterone (T) and/or normal sperm, due to disruption at one or more levels of the hypothalamic–pituitary–gonadal (HPG) axis.

Two physiologic categories:

When to suspect (Endocrine Society): evaluate only men with signs/symptoms AND unequivocally low morning T. Do not screen asymptomatic men.

Epidemiology of presentation in family medicine:

Board pearl: "Age-related low T" is a diagnosis of exclusion — always rule out reversible causes (opioids, obesity, prolactinoma, hemochromatosis, OSA) before committing a man to lifelong testosterone replacement therapy (TRT).

Step 3 management: in the ambulatory setting, anchor the workup to (1) confirm biochemical hypogonadism with two early-morning total T levels, (2) categorize primary vs secondary by LH/FSH, (3) identify and treat reversible contributors first.

Presentation Patterns and Key History

— Decreased libido, fewer spontaneous morning erections, erectile dysfunction unresponsive to PDE5i alone, decreased ejaculate volume, infertility.

— Fatigue, decreased energy, depressed mood, irritability, poor concentration, decreased exercise tolerance, hot flashes/sweats (severe deficiency), gynecomastia, decreased shaving frequency.

— Pubertal history: delayed puberty, micropenis, cryptorchidism → congenital cause (Kallmann, Klinefelter).

— Anosmia/hyposmia → Kallmann syndrome (KAL1, FGFR1 mutations).

— Medications: chronic opioids (suppress GnRH), glucocorticoids, anabolic steroids/SARMs (suppression persists months after cessation), spironolactone, ketoconazole, GnRH analogs for prostate cancer, cimetidine.

— Past testicular insult: mumps orchitis, torsion, trauma, chemo (alkylators), radiation, varicocele surgery.

— Systemic disease: HIV, ESRD, cirrhosis, hemochromatosis (joint pain, diabetes, bronze skin), sarcoidosis, hemoglobinopathies.

— Pituitary symptoms: headache, visual field defects, galactorrhea, polyuria → mass lesion or prolactinoma.

— OSA screen (STOP-BANG), weight trajectory, alcohol use.

— Fertility goals — drives whether to use TRT (suppresses spermatogenesis) versus clomiphene/hCG.

Sexual symptoms (most specific):

Non-sexual symptoms (less specific, often overlap with depression/aging):

Body composition clues: loss of muscle mass and strength, increased visceral adiposity, low-trauma osteoporotic fracture in a younger man.

Targeted history must capture:

Key distinction: Sexual symptoms cluster best with biochemical hypogonadism; isolated fatigue or low mood without sexual complaints rarely reflects true testosterone deficiency — pursue depression, sleep, thyroid, and anemia workups first.

Board pearl: A man on chronic opioids with low libido has opioid-induced hypogonadism until proven otherwise — taper opioids/rotate to buprenorphine before initiating TRT.

Physical Exam Findings

— Increased waist circumference, decreased lean muscle, decreased grip strength, sarcopenic appearance, decreased body/facial/axillary/pubic hair, fine facial wrinkling around eyes ("perioral rhytides" in long-standing deficiency).

— Gynecomastia — true glandular tissue (rubbery, concentric to nipple) vs lipomastia. Implies altered T:estradiol ratio; raises concern for Klinefelter, hCG-secreting tumor, or aromatase excess.

— Testicular volume by Prader orchidometer: normal adult 15–25 mL.

– Small, firm testes (<6 mL) → think Klinefelter.

– Small, soft testes → secondary hypogonadism (LH/FSH not stimulating).

– Asymmetric/mass → testicular tumor; obtain scrotal ultrasound.

— Penile size, Tanner staging if pubertal concerns, palpate for varicocele ("bag of worms," Valsalva), epididymal nodularity, inguinal hernias.

General/body composition:

Breast exam:

Genitourinary exam (essential, often skipped):

Visual fields by confrontation: bitemporal hemianopsia suggests pituitary macroadenoma compressing the optic chiasm — escalate to pituitary MRI.

Smell testing: anosmia → Kallmann.

Skin/joints: bronze hyperpigmentation + arthropathy of 2nd/3rd MCPs → hemochromatosis.

Cardiopulmonary: assess for untreated heart failure, signs of OSA (crowded oropharynx, large neck circumference), hepatomegaly, splenomegaly.

Prostate (DRE): baseline prior to TRT in men ≥40 — note size, nodules, asymmetry. Document baseline PSA.

Hemodynamic/volume status: generally not central, but note BP — TRT can raise BP and worsen erythrocytosis-related hyperviscosity.

Step 3 management: Document testicular volume and consistency, gynecomastia, visual fields, and DRE/PSA at the index visit — these single-handedly direct the differential between primary, secondary, and tumor-driven hypogonadism and establish prostate baseline before any TRT decision.

Diagnostic Workup — Initial Labs

— Draw total testosterone between 7–10 AM, fasting, on two separate days. T is diurnal (peaks AM) and pulsatile; a single low afternoon level is insufficient.

— Avoid testing during acute illness, hospitalization, recent high-dose glucocorticoids, or starvation — all suppress T transiently.

— Threshold (Endocrine Society 2018): total T <264 ng/dL on two AM measurements = hypogonadism in symptomatic men. Equivocal results → measure free T.

— Conditions raising SHBG (falsely "normal" total T despite low free T): aging, hyperthyroidism, HIV, anticonvulsants, estrogens, cirrhosis.

— Conditions lowering SHBG (total T may appear low despite normal free T): obesity, T2DM, nephrotic syndrome, hypothyroidism, glucocorticoids, androgens.

— Free T by equilibrium dialysis is gold standard; calculated free T (Vermeulen) acceptable. Threshold roughly <70 pg/mL.

— High LH/FSH + low T → primary (testicular).

— Low or normal LH/FSH + low T → secondary (central).

— Prolactin (rule out prolactinoma; mild ↑ with stress, dopamine antagonists).

— TSH (hypothyroidism mimics).

— Iron studies (ferritin, transferrin saturation) → hemochromatosis (saturation >45%).

— CBC (baseline hematocrit before TRT; polycythemia risk).

— PSA in men ≥40 prior to TRT.

— HbA1c, lipids, LFTs, vitamin D, 25-OH D.

— Estradiol if marked gynecomastia.

Step 1 — Confirm biochemical hypogonadism:

Step 2 — Measure free or bioavailable T when SHBG is altered:

Step 3 — Localize the lesion with LH and FSH:

Step 4 — Identify reversible/contributory causes:

Board pearl: Always repeat a low T. One-third of "low" total T values normalize on repeat — never start TRT on a single value.

Step 3 management: Order paired 8 AM total T + LH + FSH + prolactin on the second confirmatory draw to save a visit.

Advanced and Confirmatory Studies

— Pituitary MRI with contrast indicated if:

– Total T <150 ng/dL with low/normal gonadotropins

– Hyperprolactinemia

– Visual field defects, persistent headaches

– Panhypopituitarism signs (low cortisol/ACTH, central hypothyroidism, low IGF-1)

– New-onset secondary hypogonadism without obvious cause (no opioids/obesity)

— Pair MRI with full anterior pituitary panel: 8 AM cortisol/ACTH, free T4 + TSH, IGF-1, prolactin.

— Karyotype if testes are small/firm, gynecomastia, tall stature, infertility → confirm Klinefelter (47,XXY); prevalence ~1/600 men, frequently undiagnosed.

— Scrotal ultrasound for palpable testicular mass, asymmetry, or unexplained markedly elevated FSH → rule out testicular tumor.

— Semen analysis ×2 (3–7 days abstinence). Azoospermia or oligospermia changes management — avoid exogenous T entirely.

— Consider reproductive endocrinology/urology referral.

— DEXA scan in men with severe hypogonadism (T <200 ng/dL), prolonged deficiency, or low-trauma fracture. Repeat 1–2 years after initiating TRT.

— HFE gene testing if iron studies suggest hemochromatosis.

— Polysomnography for suspected OSA contributing to secondary hypogonadism.

— Hemoglobin electrophoresis if thalassemia/sickle suspected.

When LH/FSH localize to secondary (central) hypogonadism — pursue pituitary workup:

When primary hypogonadism is found:

Fertility-focused testing (if conception is a goal):

Bone health:

Other directed studies:

Key distinction: Low T + low LH + high prolactin = prolactinoma; treat with cabergoline first — prolactin normalization often restores T without need for TRT.

Board pearl: Never image the pituitary in a man with obvious obesity/opioid-driven secondary hypogonadism and normal prolactin — yield is low and incidentalomas confuse the picture.

Risk Stratification and First-Line Management Logic

— Weight loss (≥5–10% body weight): can raise total T by 50–100 ng/dL, especially with bariatric surgery.

— Taper opioids or rotate to buprenorphine (less HPG suppression).

— Treat OSA with CPAP.

— Discontinue anabolic steroids/SARMs; expect 6–18 months for recovery.

— Treat hyperprolactinemia with dopamine agonist.

— Phlebotomy for hemochromatosis.

— Optimize glycemic control, alcohol reduction, stop offending meds (glucocorticoids, ketoconazole).

— Persistent symptoms + confirmed low T despite above measures, and

— No absolute contraindications:

– Active prostate or breast cancer

– Hematocrit >50% (treat before initiating)

– Untreated severe OSA

– Uncontrolled heart failure (NYHA III/IV)

– MI, stroke, or ACS within 6 months

– Desire for fertility in the next 6–12 months → use clomiphene or hCG instead

– Palpable prostate nodule or PSA >4 (>3 if high-risk) without urology evaluation

— Discuss expected benefits (libido, energy, mood, lean mass, bone density) vs uncertain effects on mood/cognition and unproven cardiovascular benefit.

— Review risks: erythrocytosis, acne, gynecomastia, OSA worsening, infertility, possible cardiovascular signal (TRAVERSE trial showed non-inferiority for MACE but ↑ pulmonary embolism, AFib, AKI).

— Document baseline PSA, hematocrit, DRE.

Step 1 — Treat reversible causes before TRT:

Step 2 — Confirm patient is appropriate candidate for TRT:

Step 3 — Shared decision-making:

Step 3 management: Set explicit symptomatic goals (e.g., libido, morning erections, energy) and a 6-month re-evaluation point — if no symptomatic improvement despite mid-normal T, stop TRT.

Board pearl: TRT is symptom-driven therapy in confirmed biochemical hypogonadism — not a fix for fatigue alone with borderline T.

Pharmacotherapy — Testosterone Replacement Regimens

— Topical gels (1%, 1.62%, 2%): apply daily to shoulders/upper arms/abdomen.

– Pros: steady levels, easy titration, daily flexibility.

– Cons: transference to women and children — wash hands, cover application site, avoid skin-to-skin contact for ≥2 hours; FDA boxed warning.

— Intramuscular esters:

– Testosterone cypionate/enanthate 75–100 mg IM weekly or 150–200 mg every 2 weeks.

– Pros: cheap, effective.

– Cons: peak-trough swings → mood/libido fluctuation; supraphysiologic peaks raise erythrocytosis risk.

– Testosterone undecanoate IM every 10 weeks — stable levels but requires in-office observation 30 min post-injection (pulmonary oil microembolism risk; REMS).

— Subcutaneous T cypionate weekly — increasingly used; smaller needle, fewer peaks.

— Transdermal patches: daily; skin irritation common.

— Buccal/intranasal: less common; multiple daily doses.

— Subcutaneous pellets (Testopel): implanted every 3–6 months; cannot titrate once in place.

— Clomiphene citrate 25–50 mg PO daily or every other day — SERM that raises endogenous LH/FSH → T.

— hCG 1500–3000 IU SC 2–3×/week ± recombinant FSH for spermatogenesis.

— Useful for secondary hypogonadism; ineffective in primary testicular failure.

Formulations (all aim for mid-normal range, ~400–700 ng/dL):

If fertility is desired — avoid exogenous T (suppresses spermatogenesis via LH/FSH feedback):

Aromatase inhibitors (anastrozole) — not first-line; consider only in obese men with high estradiol if specialist-directed.

Step 3 management: For a typical middle-aged man without fertility plans, start T cypionate 100 mg IM or SC weekly or 1% gel 50 mg topical daily; recheck total T at 3–6 months, measured midway between injections or 2–8 hours post-gel application.

Board pearl: Counsel every man started on TRT that sperm count will fall and may not recover — a non-trivial fertility/legal consent issue.

Monitoring, Dose Adjustment, and Adjunctive Pharmacology

— 3 months, 6 months, then annually: total T, hematocrit, PSA, symptoms, adverse effects.

— Target total T mid-normal range 400–700 ng/dL.

— Hematocrit: if >54%, hold TRT, evaluate for OSA/polycythemia vera, consider therapeutic phlebotomy; resume at lower dose.

— PSA: if rise >1.4 ng/mL in 1 year or absolute >4 ng/mL (or >3 with risk factors) → urology referral before continuing.

— DEXA at baseline if severe hypogonadism; repeat at 1–2 years.

— Lipids and LFTs not routinely needed unless oral 17-α-alkylated agents used (avoid these — hepatotoxicity).

— Gel: any time after ≥1 week of stable use; ideally 2–8 hours after application.

— Weekly IM/SC cypionate: midway between injections (day 3–4).

— Long-acting undecanoate: trough, just before next injection.

— Pellets: end of dosing interval.

— Low T + low symptom response → increase dose modestly.

— Supraphysiologic T or high Hct → reduce dose or extend interval; switch to SC or gel for smoother kinetics.

— Bone: ensure calcium 1000–1200 mg + vitamin D 800–1000 IU; bisphosphonates if osteoporosis persists.

— ED: add PDE5 inhibitor if erections incomplete after T normalization.

— Gynecomastia from TRT: dose reduction, switch formulation, occasionally tamoxifen.

— Mood symptoms persist despite eugonadal T → screen for depression, treat independently.

Monitoring cadence after initiating TRT:

Timing of T measurement by formulation:

Dose adjustment principles:

Adjunctive considerations:

CCS pearl: On Step 3 CCS, after starting TRT advance the clock 3 months and order total testosterone, hematocrit, PSA, and symptom reassessment — these four are the high-yield follow-up bundle and missing any (especially hematocrit) loses points.

Special Populations — Elderly, Renal, and Hepatic Impairment

— Age-related T decline (~1–2%/year after age 40) is physiologic — treat only if clearly symptomatic with confirmed biochemical hypogonadism and reversible causes excluded.

— TRT trials (T Trials, TRAVERSE) show modest gains in sexual function, mood, anemia, and bone density; minimal cognitive benefit.

— TRAVERSE (NEJM 2023): in men 45–80 with hypogonadism and high CV risk, TRT was non-inferior for MACE but showed ↑ rates of pulmonary embolism, atrial fibrillation, and acute kidney injury.

— Start low (e.g., gel 20.25 mg daily or cypionate 50–75 mg weekly); monitor hematocrit more closely.

— Avoid TRT if recent CV event (MI/stroke within 6 months), uncontrolled HF, or severe OSA.

— Screen for fall risk, BPH symptoms (IPSS), and review polypharmacy.

— CKD contributes to secondary hypogonadism via hypothalamic suppression and hyperprolactinemia.

— TRT may improve anemia (less ESA requirement) and muscle mass.

— No dose adjustment needed for IM/topical T; monitor hematocrit closely — CKD patients are paradoxically prone to erythrocytosis on TRT.

— Avoid in ESRD with uncontrolled HTN until BP optimized.

— Avoid oral 17-α-alkylated androgens (methyltestosterone, oxandrolone) — hepatotoxicity, cholestasis, peliosis hepatis, hepatic adenoma.

— IM, transdermal, and SC formulations are safer; cirrhosis raises SHBG so interpret total T cautiously — measure free T.

— Cirrhosis itself causes hypogonadism (testicular atrophy, gynecomastia from impaired estrogen clearance).

— Compensated HF: TRT may improve exercise capacity in selected hypogonadal men.

— Decompensated/NYHA IV: avoid — fluid retention, worsened symptoms.

Older men (≥65):

Chronic kidney disease:

Hepatic impairment:

Heart failure:

Key distinction: Cirrhosis often shows low total T but normal/high SHBG and normal free T — these men generally don't need TRT; treat the liver disease and gynecomastia symptomatically.

Step 3 management: In the elderly, document explicit shared decision-making about PE/AFib/AKI risk before initiating TRT per TRAVERSE data.

Special Populations — Adolescents, Klinefelter, and Andropause Boundaries

— Constitutional delay (most common) vs pathologic hypogonadism.

— Bone age x-ray, LH/FSH, T, prolactin, TSH, IGF-1; consider GnRH stimulation testing.

— Constitutional delay: reassure or short course of low-dose T (50–100 mg IM monthly × 3–6 months) to jump-start puberty.

— Permanent hypogonadism (Kallmann, Klinefelter): gradually escalate to full adult replacement; pediatric endocrine referral.

— Initiate TRT when biochemical hypogonadism develops, typically mid-adolescence onward.

— Discuss fertility preservation — testicular sperm extraction (TESE) often successful before TRT initiation and before adulthood; coordinate with reproductive specialist.

— Higher risk of breast cancer, mediastinal germ cell tumors, osteoporosis, T2DM, autoimmune disease, venous thromboembolism — incorporate into surveillance.

— TRT virilizes; pulsatile GnRH or hCG ± FSH restores fertility when desired.

— Screen for associated anomalies: anosmia, midline defects, renal agenesis, synkinesia.

— Do not use exogenous T — suppresses spermatogenesis.

— Use clomiphene 25–50 mg PO daily/QOD or hCG ± FSH.

— Consider sperm banking before any androgen therapy.

— Distinct indication (gender-affirming therapy), not hypogonadism per se; follow WPATH/Endocrine Society dosing — typically T cypionate 50–100 mg weekly. Same monitoring (Hct, lipids, BP).

— Not a clinical syndrome by itself. Reject TRT for nonspecific aging symptoms with borderline T.

Adolescents with delayed puberty:

Klinefelter syndrome (47,XXY):

Kallmann syndrome:

Men desiring fertility (any age):

Transgender men:

"Andropause" / aging:

Board pearl: A Klinefelter adolescent who wants future fertility should be referred for microTESE before TRT — once T suppresses LH/FSH, intratesticular T falls and remaining germ cells are lost.

Step 3 management: Always document fertility intent before prescribing exogenous T at any age.

Complications and Adverse Outcomes

— Erythrocytosis — most common adverse effect. Risk highest with IM esters and in patients with OSA, smoking, COPD.

– Hct >54% → hold T, evaluate, therapeutic phlebotomy, restart at reduced dose, consider switching to gel/SC.

— VTE/PE — small but real signal (TRAVERSE); higher in first 6 months. Counsel on symptoms.

— Atrial fibrillation — increased incidence in TRAVERSE.

— Worsening of compensated HF via fluid retention.

— Hypertension — modest BP rise; monitor.

— MACE: non-inferior to placebo in TRAVERSE, settling prior concerns.

— Mild PSA rise expected (0.3–0.5 ng/mL); does not cause prostate cancer but may unmask occult disease.

— Worsened LUTS in men with significant BPH.

— Testicular atrophy, decreased spermatogenesis/azoospermia, infertility (often reversible over months–years after stopping, sometimes not).

— Gynecomastia, breast tenderness from aromatization to estradiol.

— Suppression of HPG axis — withdrawal causes profound symptomatic hypogonadism.

— Possible mild lipid changes (↓ HDL).

— Gels: transference to partners/children → virilization, premature puberty.

— Long-acting undecanoate: pulmonary oil microembolism, anaphylaxis (REMS).

— Oral alkylated agents: hepatotoxicity (avoid).

— Pellets: extrusion, infection at insertion site.

Hematologic:

Cardiovascular:

Prostate:

Sleep: worsens untreated OSA; treat OSA first.

Reproductive:

Dermatologic: acne, oily skin, accelerated male-pattern baldness.

Behavioral: irritability, mood swings (especially with peak-trough IM dosing); rarely aggression at supraphysiologic levels.

Endocrine/metabolic:

Formulation-specific:

Board pearl: A child or female partner developing virilization (acne, hirsutism, clitoromegaly) → testosterone gel transference — counsel application site coverage and handwashing at every visit.

Step 3 management: Hct >54% on TRT = stop TRT, evaluate for OSA/polycythemia, phlebotomize if symptomatic, resume at lower dose or switch to non-IM formulation.

When to Escalate Care — Consults and Inpatient Triage

— Diagnosis is unclear (discordant T levels, abnormal SHBG, equivocal symptoms).

— Pituitary lesion identified on MRI or panhypopituitarism suspected.

— Hyperprolactinemia requiring dopamine agonist titration.

— Klinefelter, Kallmann, or other congenital syndromes.

— Failure to respond to standard TRT.

— Suspected hemochromatosis with endocrine involvement.

— PSA elevation (>4, or rise >1.4 in a year), abnormal DRE/nodule.

— Significant LUTS or worsening BPH on TRT.

— Testicular mass, varicocele, or scrotal abnormality.

— Persistent ED despite eugonadal T + PDE5 inhibitor.

— Fertility desired — needs clomiphene/hCG/FSH protocols, sperm analysis, possible TESE.

— Azoospermia or severe oligospermia.

— Recent MI, stroke, ACS, or significant arrhythmia — clear TRT decision before initiation/resumption.

— New-onset AFib on TRT.

— Recurrent erythrocytosis off TRT (rule out polycythemia vera, JAK2 mutation).

— VTE on TRT — assess for thrombophilia.

— Pituitary apoplexy: sudden severe headache + vision loss + hemodynamic instability → emergent neurosurgery + stress-dose steroids.

— Symptomatic PE/DVT on TRT → admit, anticoagulate, hold T.

— New visual field defect with low T → urgent pituitary MRI; outpatient if stable, ED if rapid progression.

— Severe hyponatremia from secondary adrenal insufficiency in unrecognized panhypopituitarism — admit, IV hydrocortisone before levothyroxine.

Refer to endocrinology when:

Refer to urology when:

Refer to reproductive endocrinology/urology when:

Refer to cardiology when:

Refer to hematology when:

Inpatient triage (rare for hypogonadism itself, but watch for):

CCS pearl: A man with low T, low LH, headaches, and bitemporal hemianopsia → order pituitary MRI, full anterior pituitary panel (cortisol, ACTH, TSH, free T4, IGF-1, prolactin), neurosurgery and endocrine consults — and give hydrocortisone before thyroid hormone if adrenal insufficiency present.

Key Differentials — Within the Endocrine/HPG Axis

— Klinefelter (47,XXY): small firm testes, tall, gynecomastia, infertility, learning issues; karyotype confirms.

— Mumps orchitis: post-pubertal mumps → bilateral testicular atrophy.

— Cryptorchidism: even after orchiopexy, risk of subfertility and Leydig cell dysfunction.

— Chemotherapy (alkylators — cyclophosphamide), pelvic radiation, testicular trauma/torsion.

— Hemochromatosis: iron deposition in testes (primary) late, but pituitary (secondary) early.

— Varicocele: reversible cause of subfertility; surgical repair may improve T modestly.

— Functional/reversible (most common in primary care):

– Obesity, metabolic syndrome, T2DM — weight loss restores T.

– Chronic opioids — even low-dose chronic opioids suppress GnRH.

– Chronic glucocorticoids, anabolic steroid abuse, marijuana (variable), alcohol.

– OSA, severe systemic illness, malnutrition.

— Structural pituitary disease:

– Prolactinoma (most common secretory adenoma) — low T + low LH + high prolactin.

– Nonfunctioning macroadenoma, craniopharyngioma.

– Pituitary apoplexy, Sheehan syndrome (rare in men), trauma, radiation, surgery.

– Hypophysitis (autoimmune, IgG4, checkpoint-inhibitor-induced).

— Congenital GnRH deficiency: Kallmann (with anosmia), idiopathic hypogonadotropic hypogonadism.

— Hemochromatosis: earliest endocrine manifestation often pituitary gonadotrope dysfunction.

Primary (testicular) hypogonadism mimics and causes:

Secondary (central) hypogonadism causes:

Key distinction: Low T + mildly elevated prolactin (<100 ng/mL) often reflects stalk effect from a nonfunctioning macroadenoma; low T + prolactin >200 ng/mL strongly suggests prolactinoma — and dopamine agonist (cabergoline) is first-line, not surgery.

Board pearl: New checkpoint inhibitor (ipilimumab, pembrolizumab) + central hypogonadism → think immune-related hypophysitis; obtain pituitary MRI and full anterior pituitary panel.

Key Differentials — Conditions That Mimic Hypogonadism

— Low libido, fatigue, anhedonia, decreased motivation, decreased energy.

— PHQ-9 ≥10 — treat depression first; reassess sexual function after.

— T does not consistently improve mood independent of depression treatment.

— Fatigue, weight gain, low libido, ED, low energy; can also lower SHBG/total T.

— Check TSH on every hypogonadism workup; treating hypothyroidism may normalize T.

— Fatigue, exercise intolerance — CBC distinguishes; iron studies if microcytic.

— Fatigue, decreased libido, ED, morning headaches; itself causes secondary hypogonadism. Treat OSA first.

— All produce fatigue/sarcopenia and can lower T. Treat underlying disease.

— SSRIs, beta-blockers, thiazides, finasteride, spironolactone, opioids — sexual side effects; review med list before labeling as hypogonadism.

— Atherosclerotic ED in diabetic/hypertensive men with normal T — treat with PDE5i, optimize CV risk factors.

— ED is a marker for subclinical CAD — check lipids, BP, glucose, consider stress testing in symptomatic men.

— Fatigue, weakness, weight loss; may coexist with secondary hypogonadism in panhypopituitarism.

— Antipsychotics (risperidone, haloperidol), metoclopramide, methadone — mimic prolactinoma. Stop drug → reassess.

— Truncal obesity, weakness, low libido — suppresses HPG axis; screen if features present.

Symptoms of low T overlap heavily with other diagnoses — always consider:

Depression and anxiety:

Hypothyroidism:

Anemia:

Obstructive sleep apnea:

Chronic kidney disease, cirrhosis, HF, COPD:

Medication effects without true hypogonadism:

Erectile dysfunction of vascular/neurogenic origin:

Adrenal insufficiency:

Hyperprolactinemia from drugs:

Hypercortisolism (Cushing):

Key distinction: Fatigue + low libido + normal AM total and free T is not hypogonadism — pursue depression, OSA, thyroid, anemia, and medication review instead of empirically prescribing TRT.

Step 3 management: Before any TRT script, document negative screens for depression (PHQ-9), OSA (STOP-BANG), thyroid (TSH), and anemia (CBC) — these are the four common Step 3 distractors.

Secondary Prevention and Long-Term Plan

— Weight loss 5–10% (Mediterranean/DASH dietary pattern, caloric deficit).

— Aerobic exercise 150 min/week + resistance training 2×/week — independently raises T and improves body composition.

— Sleep hygiene; treat OSA with CPAP.

— Limit alcohol (<2 drinks/day), avoid marijuana, no anabolic steroids.

— Smoking cessation.

— Reassess continued indication annually — does the patient still derive symptomatic benefit?

— Discontinue trial if no symptomatic improvement at 6 months despite mid-normal T.

— Update fertility goals at each visit; transition to clomiphene/hCG if conception sought.

— ASCVD risk assessment, lipid management, BP control, glucose control — TRT does not replace these.

— Aspirin per primary prevention guidelines.

— TRAVERSE-informed counseling: small but real ↑ in AFib, PE, AKI — patients should report calf swelling, dyspnea, palpitations.

— Calcium 1000–1200 mg/day, vitamin D 800–1000 IU/day.

— DEXA at baseline (severe hypogonadism), repeat 1–2 years on TRT.

— Bisphosphonate if osteoporosis persists despite eugonadal T.

— Continue shared-decision-making prostate cancer screening per USPSTF (age 55–69, biennial PSA).

— Annual DRE in men on TRT is reasonable.

Lifestyle is foundational — applies to all hypogonadal men regardless of TRT:

Long-term TRT plan (if indicated):

Cardiovascular risk reduction:

Bone health:

Prostate health:

Vaccinations and preventive care: standard age-based — TRT does not change schedule.

Mental health follow-up: depression and anxiety often persist; screen annually.

Key distinction: TRT corrects biochemistry and many symptoms but is not cardiovascular protective and does not treat depression — keep these in separate management buckets.

Step 3 management: At every annual visit, repeat the four-point bundle: symptom assessment, total T, hematocrit, PSA — and reaffirm shared decision-making to continue therapy.

Follow-Up, Monitoring Parameters, and Counseling

— 3 months: total T (timed to formulation), hematocrit, PSA, symptom review, side effects, application/injection technique.

— 6 months: same panel + DRE; decide whether to continue therapy based on symptomatic benefit.

— 12 months and annually thereafter: total T, hematocrit, PSA, DRE, lipid panel, BP, weight, screen for OSA worsening.

— DEXA at baseline (if indicated) and at 1–2 years.

— Hct >54%: hold T, phlebotomize, evaluate OSA/PCV, restart at lower dose.

— PSA >4 (or >3 with risk factors), rise >1.4 ng/mL in 1 year, or new nodule: urology referral before continuing.

— Total T >800 ng/dL: reduce dose or extend interval.

— Persistent symptoms with mid-normal T: reassess diagnosis; consider depression, OSA, thyroid.

— Fertility: TRT suppresses spermatogenesis; if conception desired, switch to clomiphene/hCG.

— Transference (gels): wash hands, cover application site, avoid skin contact for ≥2 h; risk to women and children.

— VTE/PE symptoms: unilateral leg swelling, pleuritic chest pain, dyspnea — seek care.

— Mood and aggression: report unusual irritability or mood swings.

— Don't share T; controlled substance (Schedule III in US).

— Lifestyle adherence: TRT augments but doesn't replace diet/exercise/sleep.

Visit cadence after TRT initiation:

Specific thresholds requiring action:

Counseling pillars (revisit at each visit):

Rehab considerations: structured resistance training program optimizes lean mass gains; refer to physical therapy or supervised program in deconditioned or elderly men.

Discontinuation counseling: stopping TRT after months/years → withdrawal symptoms (fatigue, low libido, hot flashes) lasting weeks; endogenous axis may take 3–12 months to recover, sometimes never.

Board pearl: Always measure TRT bloodwork timed to the formulation — a random level on a weekly cypionate patient can be either peak or trough and misleads dosing.

Step 3 management: Schedule the 3-month follow-up at the time of initial prescription — not doing so is a common Step 3 transition-of-care error.

Ethical, Legal, and Patient Safety Considerations

— Document discussion of infertility risk (potentially permanent) — particularly critical in young men; offer sperm banking if family planning may be future consideration.

— Document discussion of CV risk per TRAVERSE (non-inferior MACE but ↑ AFib, PE, AKI).

— Discuss prostate cancer screening implications.

— Discuss erythrocytosis, OSA worsening, gynecomastia.

— Address transference risk to women/children with gels — written and verbal counseling, documented.

— Testosterone is DEA Schedule III — comply with state PDMP checks, e-prescribing rules, and refill limits.

— Counsel patients not to share or supplement with non-prescribed androgens.

— Many patients arrive on inappropriately initiated TRT without confirmed biochemical hypogonadism or workup. Discuss reassessment; do not blindly continue.

— Confirm two AM T levels, LH/FSH, prolactin, hematocrit, PSA — sometimes the diagnosis is wrong.

— Patient confidentiality applies; counsel on health risks, fertility loss, hepatotoxicity, mood effects. Do not report to employers/athletic bodies without consent unless mandated.

— Communicate TRT status clearly at hospitalization, surgery, and primary care handoffs — perioperative hold not generally required, but inform anesthesia (VTE risk).

— On hospital discharge, ensure outpatient PCP knows TRT regimen, last labs, and next monitoring date — TRT continuation without monitoring is a patient safety gap.

Informed consent — required elements before TRT:

Controlled substance prescribing:

Direct-to-consumer "low-T clinics":

Anabolic steroid use disclosure:

Transitions of care:

Adolescents: parental consent required for minors; balance autonomy as adolescence progresses, especially around fertility preservation discussions.

Mandatory reporting: suspected child virilization from T gel transference may rise to a safety report depending on circumstances; counsel on safe storage.

Step 3 management: A young man on TRT from a "men's clinic" with no documented workup → stop TRT, perform full workup, re-counsel, and re-consent before any continuation. This is the canonical Step 3 stem.

High-Yield Associations and Rapid-Fire Clinical Facts

Klinefelter (47,XXY): tall, small firm testes, gynecomastia, infertility, learning differences, ↑ breast cancer, ↑ mediastinal germ cell tumor, ↑ VTE, ↑ T2DM, ↑ osteoporosis.

Kallmann syndrome: hypogonadotropic hypogonadism + anosmia + midline defects (cleft palate, renal agenesis, synkinesia). KAL1, FGFR1.

Hemochromatosis: pituitary gonadotrope dysfunction is earliest endocrine sign; transferrin saturation >45%, ferritin elevated; treat with phlebotomy.

Prolactinoma: low T + low LH + high prolactin → cabergoline first, not surgery.

Chronic opioid use: dose- and duration-dependent suppression of GnRH → secondary hypogonadism; consider buprenorphine.

Anabolic steroid abuse: suppressed LH/FSH/T after cessation; recovery 6–18 months; spermatogenesis may not return.

Obesity: ↑ aromatase → ↑ estradiol → suppresses LH; weight loss reverses.

TRAVERSE (NEJM 2023): TRT non-inferior for MACE; ↑ AFib, PE, AKI.

Erythrocytosis cutoff: Hct >54% → hold/dose-reduce.

T measurement timing: weekly IM cypionate → midpoint (day 3–4); gel → 2–8 h post-application; undecanoate → trough.

Fertility preservation: exogenous T suppresses spermatogenesis — use clomiphene or hCG/FSH.

TRT contraindications: active prostate or breast cancer; Hct >50% pretreatment; severe untreated OSA; uncontrolled HF; MI/stroke <6 months; planning fertility <12 months.

Pituitary MRI indications: T <150 ng/dL, hyperprolactinemia, visual field defects, panhypopituitarism, unexplained secondary hypogonadism.

Adolescent constitutional delay: short course low-dose IM T; bone age delayed but linear.

Cirrhosis: elevated SHBG, low total T, often normal free T — usually no TRT needed.

Checkpoint inhibitor hypophysitis: secondary hypogonadism + other anterior pituitary deficits; replace cortisol first.

Step 3 management: Memorize the "start TRT" checklist: confirmed AM T ×2, LH/FSH/prolactin, PSA, DRE, Hct, fertility goals, contraindications screened, shared decision-making documented.

Board pearl: Tall man + small firm testes + gynecomastia + infertility = Klinefelter until karyotype proves otherwise.

Board Question Stem Patterns

Stem 1 — Confirm before treating: 45-year-old with fatigue and low libido; afternoon T = 220 ng/dL. Next step? → Repeat total T at 8 AM × 2, add LH/FSH/prolactin. Not start TRT.

Stem 2 — Reversible cause: 38-year-old on chronic methadone with low T and low LH. Next step? → Address opioid therapy (taper, rotate to buprenorphine) before TRT.

Stem 3 — Prolactinoma: Low T, low LH, prolactin 350 ng/mL, bitemporal hemianopsia. Best next step? → Pituitary MRI + cabergoline (not transsphenoidal surgery first, not TRT).

Stem 4 — Klinefelter: Tall 17-year-old, small firm testes, gynecomastia, high LH/FSH, low T. Diagnostic test? → Karyotype. Management consideration if future fertility desired? → Sperm retrieval/TESE before TRT.

Stem 5 — TRT contraindication: 62-year-old with low T and recent NSTEMI 2 months ago. Next step? → Defer TRT for ≥6 months, optimize CV care.

Stem 6 — Fertility-desiring man: 32-year-old with low T, normal LH/FSH, wants to conceive. Best therapy? → Clomiphene 25–50 mg PO daily/QOD (NOT exogenous T).

Stem 7 — Erythrocytosis: 58-year-old on T cypionate × 1 year, Hct 56%, asymptomatic. Next step? → Hold TRT, evaluate for OSA, therapeutic phlebotomy, then resume at lower dose or switch to gel.

Stem 8 — Transference: 4-year-old daughter develops pubic hair while father uses 1% T gel. Diagnosis? → Testosterone transference; counsel application site coverage, handwashing, skin-to-skin avoidance.

Stem 9 — Hemochromatosis: 50-year-old with low T, low LH, diabetes, arthropathy. Best next test? → Iron studies (transferrin saturation, ferritin), then HFE genotyping.

Stem 10 — TRT monitoring: Man started on weekly cypionate 12 weeks ago. When/what to measure? → Total T midweek, hematocrit, PSA, symptoms at 3 months.

Stem 11 — TRAVERSE-flavored stem: Symptomatic hypogonadism with high CV risk — counsel on PE, AFib, AKI risk; MACE non-inferior.

CCS pearl: When the stem screams "fatigue and low libido" on Step 3, the right first move is two AM T levels, not an MRI or TRT prescription.

One-Line Recap

Male hypogonadism is symptomatic androgen deficiency requiring confirmation with two early-morning total testosterone levels, classification by LH/FSH into primary vs secondary, exclusion of reversible causes (opioids, obesity, OSA, prolactinoma, hemochromatosis), and individualized testosterone replacement only after contraindications are excluded, fertility goals are addressed, and baseline PSA/hematocrit are documented.

Workup essentials: AM total T ×2 → if low, add LH/FSH/prolactin/iron studies/TSH/PSA/Hct; pursue free T when SHBG is altered; pituitary MRI for T <150, hyperprolactinemia, visual field defects, or unexplained central hypogonadism.

Treatment essentials: Fix reversible causes first (weight loss, opioid taper, OSA treatment, cabergoline for prolactinoma); TRT only if persistent symptoms + biochemical hypogonadism + no contraindications + no fertility desire; use clomiphene or hCG/FSH when fertility is the goal.

Monitoring essentials: At 3 months, 6 months, then annually — total T (timed to formulation), hematocrit (hold/adjust if >54%), PSA (urology if >4 or rise >1.4/year), symptom benefit (stop if none at 6 months), DEXA in severe hypogonadism, BP, lipids.

Step 3 essentials: Document shared decision-making per TRAVERSE (non-inferior MACE; ↑ PE/AFib/AKI), counsel on gel transference and infertility, never start TRT on a single afternoon T, and re-evaluate any "low-T-clinic" prescription before continuing — these are the highest-yield Step 3 traps in this topic.