Testosterone Cypionate Side Effects: Potentially Permanent Adverse Events Explained

Which effects does the label actually call lasting?

The Depo-Testosterone label, the branded cypionate product, makes one clear statement about persistence: 'Gynecomastia may develop and occasionally persists in patients being treated for hypogonadism' [1].

For fertility, the Depo-Testosterone label describes a mechanism rather than a verdict. Endogenous testosterone release is inhibited through feedback inhibition of pituitary luteinizing hormone (LH), and at large doses also follicle-stimulating hormone (FSH), so sperm production may be suppressed and sperm count may fall [1]. The label for Azmiro, a different testosterone cypionate injection, says reduced fertility is seen in some men on testosterone replacement and that the effect may be irreversible.

The Depo-Testosterone label's drug abuse section lists testicular atrophy, subfertility and infertility among reactions reported in people who abuse anabolic androgenic steroids, typically at doses above those prescribed and often in combination with other steroids [1].

Sperm production: how often does it come back?

Most of the recovery numbers come from hormonal male contraception research in healthy, fertile men, not from men on replacement doses.

An integrated analysis pooled 30 studies and 1,549 healthy eugonadal men on hormonal contraceptive regimens. Median time for sperm concentration to return to 20 million/mL was 3.4 months; 67% reached that threshold within 6 months, 90% within 12 months, 96% within 16 months and 100% within 24 months [3]. Recovery was faster with shorter-acting testosterone preparations, shorter treatment, older age and a higher baseline sperm count [3].

A World Health Organization multicenter study gave 271 healthy fertile men 200 mg of testosterone enanthate weekly. Azoospermia developed in 157 men, a cumulative rate of 65% at 6 months. After injections stopped, the estimated median time from azoospermia back to 20 million/mL was 3.7 months, and to each man's own baseline concentration 6.7 months [4].

In a retrospective series of 49 men who had azoospermia or severe oligospermia (under 1 million/mL) while taking exogenous testosterone, sperm production returned or improved in 47 of them (95.9%) after hCG 3,000 units subcutaneously every other day plus clomiphene, tamoxifen, anastrozole or recombinant FSH. The average time was 4.6 months, with a mean first density of 22.6 million/mL [5]. A second series of 66 men with infertility after testosterone use stopped testosterone and received high-dose hCG plus a selective estrogen receptor modulator; 70% reached a total motile count above 5 million within 12 months, 64.8% of the azoospermic men did versus 91.7% of the cryptozoospermic men, and older age and longer testosterone use predicted slower recovery [6].

These figures come from healthy volunteers and from retrospective series of men treated for infertility, so they do not give a rate of lasting infertility for men on replacement doses. The Endocrine Society's 2018 guideline recommends against starting testosterone therapy in men who plan to have children in the near term [7].

Testicular atrophy

Testosterone suppresses pituitary LH release, and at large doses also FSH [1]. The Depo-Testosterone label reports testicular atrophy among reactions seen in people who abuse anabolic androgenic steroids, and it does not say whether testicular size returns after stopping [1].

Gynecomastia

Breast tissue is a balance between estrogen, which stimulates growth, and androgens, which inhibit it; most gynecomastia comes from deficient androgen action or excessive estrogen action in breast tissue [8]. Testosterone is converted to estradiol by the enzyme aromatase, so raising testosterone raises estradiol [9].

The label's warning is that gynecomastia may develop and occasionally persists [1]. A review says surgery to remove the tissue may be necessary when breast enlargement does not resolve spontaneously or with medical therapy [8]. Breast carcinoma in men is a listed contraindication to Depo-Testosterone [1].

Male pattern baldness

The Depo-Testosterone label lists hirsutism, male pattern of baldness, seborrhea and acne among reported skin reactions [1]. It gives no rate and says nothing about whether hair regrows after the drug is stopped. The label does note that in many tissues testosterone activity appears to depend on reduction to dihydrotestosterone, the more potent androgen [1].

Hematocrit and polycythemia

The Depo-Testosterone label says to check hemoglobin and hematocrit periodically during long-term use [1].

How much hematocrit rises depends partly on the route. A network meta-analysis of 29 placebo-controlled randomized trials and 3,393 men found intramuscular testosterone enanthate or cypionate raised mean hematocrit by 4.0 percentage points (95% CI 2.9 to 5.1) versus placebo, gel by 3.0, patch by 1.4, oral testosterone undecanoate by 4.3 and intramuscular undecanoate by 1.6 [2].

A retrospective review of 178 hypogonadal men followed for 3 years found erythrocytosis, defined as hematocrit above 50%, in 66.7% of men on injectable testosterone, 12.8% on gels and 35.1% on pellets. The injection group was younger (mean 42.5 versus about 54 years) and started with higher baseline hematocrit, and the study was not randomized [10]. A review of the same literature estimated that men on testosterone replacement had a 315% greater risk of erythrocytosis (hematocrit above 0.52) than controls, with injectables contributing the most [11].

The Depo-Testosterone label reports venous thromboembolism, including deep vein thrombosis and pulmonary embolism, and says to discontinue treatment and begin a workup if such an event is suspected [1]. Whether testosterone-related increases in hematocrit lead to those events remains unclear [12][11].

Blood pressure and the heart

The Depo-Testosterone label states that long-term clinical safety trials have not been conducted for cardiovascular outcomes, that epidemiologic studies and randomized trials have been inconclusive for major adverse cardiovascular events, and that some studies, but not all, have reported an increased risk [1]. It also warns that testosterone can increase blood pressure, which can raise cardiovascular risk over time, that blood pressure should be monitored periodically, and that testosterone products are not recommended in uncontrolled hypertension [1].

In February 2025, FDA announced class-wide labeling changes: adding TRAVERSE results to testosterone labels, removing boxed-warning language about increased cardiovascular risk, and adding a blood pressure warning where one was missing; the agency said ambulatory monitoring confirmed a blood pressure increase with all testosterone products [13]. The Depo-Testosterone label does not mention TRAVERSE, and it carries no boxed warning [1].

The largest outcome trial, TRAVERSE, randomized 5,246 men aged 45 to 80 with hypogonadism and existing or high cardiovascular risk to daily 1.62% testosterone gel or placebo. Major adverse cardiovascular events occurred in 7.0% on testosterone versus 7.3% on placebo, hazard ratio 0.96 (95% CI 0.78 to 1.17), meeting noninferiority [14]. That trial tested a gel; no outcome trial of comparable size exists for injectable testosterone [14].

Liver and injection sites

The label says prolonged use of high doses of androgens has been associated with hepatic adenomas, hepatocellular carcinoma and peliosis hepatis, all potentially life-threatening, and attributes these principally to the 17-alpha-alkyl androgens [1]. It also lists cholestatic jaundice and liver function test changes among reported reactions [1]. Injection site pain and inflammation are listed among reported reactions [1].