What causes low testosterone in men?
Low testosterone is caused by primary testicular dysfunction, secondary (hypothalamic-pituitary) signaling failure, age-related decline, metabolic dysfunction, chronic stress, sleep deprivation, certain medications, or a combination. The biomarker panel and provider review identify which vector is dominant.
Full answer
Low testosterone is rarely a single-cause condition. The dominant clinical vectors are: primary hypogonadism (testicular dysfunction — surgery, trauma, genetic, autoimmune, chemotherapy), secondary hypogonadism (failure of the hypothalamic-pituitary axis to signal — pituitary lesions, opioid use, severe stress, hyperprolactinemia), age-related decline (the gradual drift starting in the 30s and 40s), metabolic dysfunction (obesity, insulin resistance, fatty liver — adipose tissue aromatizes testosterone to estradiol and suppresses the HPG axis), chronic sleep deprivation (testosterone is largely produced during slow-wave sleep), and medication effects (chronic opioids, glucocorticoids, certain antifungals and antiandrogens). The standardized biomarker panel — total and free testosterone, SHBG, LH, FSH, estradiol, prolactin, thyroid, glucose, lipids — is read together with symptoms and history to surface which vector is dominant before a pathway is recommended.
Educational. Not a substitute for individualized provider review.
- Testosterone optimization pathway — Primary source · oMeds
- Testosterone reference — Reference · oMeds Learn
- Fatigue & recovery — Reference · oMeds Learn
- Reviewed by Dr. Laura Purdy, MD, MBA · Clinical Director, oMeds · Last reviewed 2026-05-29