Male hypogonadism is a clinical syndrome resulting from failure of the testes to produce adequate testosterone, sperm, or both. Low testosterone (often called "low T") is extremely common, affecting an estimated 2–6 million American men. Symptoms are often non-specific, but when truly due to testosterone deficiency, treatment is effective.
Classification
- Primary hypogonadism: The testes themselves fail — despite high LH/FSH signals from the pituitary. Causes include Klinefelter syndrome (47,XXY), testicular injury or surgery, chemotherapy/radiation, undescended testes, and autoimmune damage.
- Secondary hypogonadism: The pituitary or hypothalamus fails to signal the testes (low LH/FSH despite low testosterone). Causes include pituitary tumors, hyperprolactinemia, obesity, opioid use, anabolic steroid use, hemochromatosis, and severe illness.
Symptoms
The symptoms of low testosterone are non-specific and overlap with many other conditions. Classic symptoms include:
- Decreased libido (reduced sex drive)
- Erectile dysfunction
- Fatigue and decreased energy
- Decreased muscle mass and strength
- Increased body fat, particularly in the abdomen
- Decreased bone density (osteoporosis risk)
- Depressed mood and irritability
- Decreased body and facial hair
- Infertility
- Hot flashes (in severe/acute cases)
- Reduced testicular volume
⚠️ Important: Fatigue, decreased libido, and mood changes are extremely common in men and have many causes. A diagnosis of hypogonadism requires both symptoms AND confirmed low testosterone on two separate morning blood tests — not just symptoms alone.
Diagnosis
Proper diagnosis requires:
- Morning (7–10 AM) total testosterone: Testosterone peaks in the morning and declines through the day. Two separate morning tests are needed to confirm a low result.
- LH, FSH: Distinguish primary from secondary hypogonadism
- SHBG, calculated free testosterone: Important in men with borderline total T or obesity
- Prolactin, iron studies: Evaluate for secondary causes
- Pituitary MRI: If secondary hypogonadism is suspected
Testosterone Replacement Therapy (TRT)
When low testosterone is confirmed along with compatible symptoms, TRT is highly effective. Options include:
- Topical gels or creams (AndroGel, Testim): Applied daily; easy to use; skin transfer to partners/children is a concern
- Injections (testosterone cypionate/enanthate): Given every 1–2 weeks (self-administered) or every 10 weeks (Aveed, clinic-administered)
- Pellets (Testopel): Implanted under the skin every 3–6 months
- Patches, buccal, nasal: Less commonly used
TRT impairs sperm production and fertility — men who want to father children should not use TRT. Alternative treatments (clomiphene, hCG, FSH) can raise testosterone while preserving fertility.
Monitoring
Regular monitoring includes testosterone levels, hematocrit (TRT increases red blood cell production), prostate health (PSA), and symptom assessment.
Key Takeaways
- Hypogonadism requires both symptoms AND two confirmed low morning testosterone levels for diagnosis
- Symptoms are non-specific — many men with these symptoms have normal testosterone
- Primary hypogonadism originates in the testes; secondary in the pituitary/hypothalamus
- TRT is effective but impairs fertility — men wanting children need alternative treatments
- An endocrinologist ensures proper diagnosis and rules out treatable secondary causes
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