Testosterone Cypionate After Bariatric Surgery: What Patients and Clinicians Need to Know

What happens to testosterone after bariatric surgery?

A 12-month observational study followed 33 men with morbid obesity (mean BMI 50.3) through bariatric surgery [1]. Before surgery, 78.8% had low total testosterone (below 300 ng/dL) and 51.5% low free testosterone. After a mean weight loss of 18.8%, total testosterone, free testosterone, SHBG and FSH rose, and estradiol and prolactin fell. One year out, 6% still had low total testosterone and 15% low free testosterone, and the authors concluded that obesity-associated hypogonadism is mostly reversed by sustained weight loss [1]. The study measured hormone changes before and 12 months after surgery; it did not evaluate testosterone cypionate treatment [1].

Does gastric bypass change how testosterone cypionate is absorbed?

Testosterone cypionate is an oil-soluble ester of testosterone. The Depo-Testosterone label says testosterone esters in oil injected intramuscularly are absorbed slowly from the lipid phase, gives a half-life of about eight days, and says cypionate can be given at intervals of two to four weeks [2]. The label does not provide bariatric-specific absorption data [2].

What does the label say about dosing and monitoring?

The Depo-Testosterone dosing section gives no bariatric-specific instructions. The label says to confirm hypogonadism before starting, with serum testosterone measured in the morning on at least two separate days and both values below the normal range. For replacement in hypogonadal men it describes 50 to 400 mg every two to four weeks, given deep in the gluteal muscle, and says it should not be given intravenously [2]. Listed contraindications include breast cancer, known or suspected prostate cancer, pregnancy, and serious cardiac, hepatic or renal disease [2].

Polycythemia is a listed adverse reaction, and the label advises periodic hemoglobin and hematocrit checks during long-term use. It reports venous thromboembolism with testosterone products and says to discontinue treatment if it is suspected [2]. Across 29 placebo-controlled randomized trials (3,393 men), intramuscular enanthate or cypionate raised mean hematocrit by 4.0% versus placebo (95% CI 2.9 to 5.1) [3]. The label also states that testosterone can raise blood pressure and that testosterone products are not recommended in patients with uncontrolled hypertension [2].

What about fertility?

Exogenous testosterone inhibits pituitary luteinizing hormone and, at large doses, follicle-stimulating hormone, which suppresses sperm production [2]. The Endocrine Society recommends against starting testosterone therapy in men planning fertility in the near term [4]. In a retrospective series of 66 men given hCG plus a selective estrogen receptor modulator after stopping testosterone, 70% reached a total motile count above 5 million within 12 months, and older age and longer testosterone use predicted slower recovery [5].