Diagnostic Workup of Suspected Hypogonadism
Click each step to expand the rationale and key decision points. The workup follows Endocrine Society guidance, adapted by Dr. Rajpal for the MOSH patient.
01History & Physical — Symptoms and Signs
Establish whether the patient has clinical features of hypogonadism. Specific signs (small testes, eunuchoid features) carry the most weight. Suggestive signs (low libido, ED) are common but nonspecific. Nonspecific symptoms alone are insufficient.
Pitfall: labs without symptoms = not hypogonadism, regardless of the number.
02Morning Total T (8 AM, fasting)
Diurnal variation is real. Test in the patient's morning — for night shift workers, that means after their shift, not 8 AM clock time.
Lab normal range: 250-1100 ng/dL.
Normal total T? Hypogonadism essentially ruled out (unless high SHBG suspected — see step 3).
03Suspect altered SHBG? Check Free T
Obesity is the most common cause of low SHBG, which lowers total T artifactually.
Always check free T when: obesity is present, total T is borderline (250-300 ng/dL), or any SHBG-altering condition is suspected.
Bioavailable T (free + albumin-bound) is the most accurate functional measure.
04Repeat Low T + Add LH and FSH
Endocrine Society requires "unequivocally and consistently low" — a single low value is not enough. Always repeat to confirm.
LH and FSH localize the problem:
• Low/normal LH+FSH → secondary (hypothalamic/pituitary) — includes MOSH
• High LH+FSH → primary (testicular) — Klinefelter, post-orchitis, testicular insult
05Classify and Investigate Cause
Secondary causes: obesity/T2DM/MetS (functional), pituitary/hypothalamic disease (organic), opioids, glucocorticoids, marijuana, severe acute illness.
Primary causes: Klinefelter (karyotype), prior chemo/radiation, orchitis, trauma, advanced age.
MRI in selected cases: severe hypogonadism (T < 150 ng/dL), visual symptoms, hyperprolactinemia, low cortisol/free T4.
06Semen Analysis if Fertility Concern
Critical step before any TRT. TRT suppresses spermatogenesis — once started in a fertility-seeking patient, you've narrowed his options.
Document baseline volume, count, motility, morphology.