Male Hypogonadism
Male hypogonadism is testosterone deficiency with associated symptoms, classified as primary (testicular) or secondary (pituitary/hypothalamic), per the Endocrine Society Clinical Practice Guideline (2018).
Symptoms
Specific symptoms (reduced libido, erectile dysfunction, loss of body hair) carry more diagnostic weight than nonspecific ones (fatigue, low mood) -- the guideline is explicit that vague symptoms alone shouldn't prompt testing.
Causes and risk
Obesity is the leading reversible cause of secondary hypogonadism in men; aging, pituitary disorders, and primary testicular conditions (including prior chemotherapy or genetic conditions like Klinefelter syndrome) also cause it.
How it is evaluated
Fasting morning testosterone (7-10 AM), confirmed on a second sample, with LH/FSH to distinguish primary from secondary. Pituitary MRI is triggered by testosterone under 150 ng/dL, elevated prolactin, or headache/visual changes.
Treatment
Weight loss is first-line for obesity-related hypogonadism and often restores testosterone without medication. Testosterone therapy is reserved for confirmed, symptomatic, non-reversible deficiency, with hematocrit and testosterone monitored at 3-6 months then annually.
When to seek care
Headache with visual changes (possible pituitary mass), or signs of a blood clot while on testosterone therapy, need prompt evaluation.