Low Testosterone

Low Testosterone: Evaluation

Testosterone deficiency: low production + signs/symptoms
Lab cutoff: < 300ng/dL
Testosterone therapy: replacement therapies and therapies that stimulate endogenous testosterone production
Success: improved levels to 450-600ng/dL + improvement/resolution of signs/symptoms

Symptoms: fatigue, reduced energy/endurance, depression, poor concentration/memory, irritability, reduced sex drive, erectile dysfunction, history infertility, visual field changes, anosmia
Signs: body habitus, body hair patterns, gynecomastia, decreased muscle mass
Associated conditions: obesity (BMI > 40), anemia, low bone density, DM, testis/pelvic XRT, HIV, infertility, pituitary dysfunction
Medications: spironolactone, ketoconazole, ADT, marijuana, steroids, opioids, chemotherapy
Questionnaires: currently none exist that are proven to be beneficial

Primary testicular failure: Klinefelter syndrome, Noonan syndrome, absent testes, poorly functioning testes
Secondary testicular failure: Kallmann syndorme, exogenous androgen, hyperprolactinemia, hemochormatosis, opioid use, pituitary/hypothalamic injury, Prader-Willi syndrome, Laurence-Moon-Bardet-Biedl syndrome (hypogonadism + polydactly + retinitis pigmentosa)

Tips: confirm low T on 2+ tests on separate occasions, draw lab between 3-8AM (if sleep cycle 10PM-6AM), illness can cause decreased testosterone, draw albumin and SHBG to assess bioavailable T
If proven low T: draw LH (hypogonadotropic hypogonadism)
If low T + low LH: draw prolactin (prolactinoma)
If gynecomastia or other breast symptoms: check estrogen (may worsen symptoms)
Other tests: check baseline CBC, PSA if > 40yo, and consider DEXA, FSH, HbA1c, karyotype in individually indicated patients

Evaluation: check prolactin levels x2 (can be randomly elevated)
Non-prolactinoma causes: renal failure, liver failure, hypothyroid, estrogen use, stress, medications
Workup: check brain MRI to assess for prolactinoma
Bromocriptine: dopamine agonist, can improve libido and erections
Prolactinoma: most commonly presents with reduced libido and ED, can try bromocriptine, otherwise XRT/surgery, testosterone may not normalize after treatment

Effect: increased levels decrease free and bioavailable testosterone (tightly binds, does not exert biological effect)
Decreased SHBG: hypothyroid, obesity, nephrotic syndrome, DM, acromegaly, steroids
Increased SHBG: liver disease, estrogen use, hyperthyroid, HIV, seizure meds, smoking, aging

AUA Core Curriculum
Burnett, A. and R. Ramasamy. "Evaluation and Management of Erectile Dysfunction." Campbell-Walsh Urology 12 (2020).
Mulhall, John P., et al. "Evaluation and management of testosterone deficiency: AUA guideline." The Journal of urology 200.2 (2018): 423-432.
Ory, Jesse, et al. "Secondary polycythemia in men receiving testosterone therapy increases risk of major adverse cardiovascular events and venous thromboembolism in the first year of therapy." The Journal of urology 207.6 (2022): 1295-1301.
Wieder JA: Pocket Guide to Urology. Sixth Edition. J.Wieder Medical: Oakland, CA, 2021.