Testosterone Cypionate

• Male Hypogonadism
• Testosterone Deficiency
• Primary Hypogonadism

Testosterone cypionate (Depo-Testosterone) is a long-acting injectable form of testosterone used as replacement therapy in adult men with confirmed primary or secondary hypogonadism. The cypionate ester slows hydrolysis of testosterone after intramuscular injection, allowing dosing every one to two weeks while maintaining serum levels in or near the physiologic range. It is one of the longest-used and most extensively prescribed androgen formulations in the United States. As a Schedule III controlled substance, it requires careful diagnosis, patient counseling, and structured follow-up. It is prescribed by primary care, endocrine, and urologic specialists and is not a wellness or anti-aging product.

Mechanism of Action

Testosterone is the principal endogenous androgen in men. It binds the androgen receptor in target tissues including muscle, bone, brain, sebaceous glands, hair follicles, and the prostate. Activation of the androgen receptor regulates transcription of genes that maintain libido, erectile function, muscle mass, fat distribution, bone mineral density, hematopoiesis, mood, and energy. A portion of circulating testosterone is converted by aromatase to estradiol, which has its own essential roles in bone health, cognition, and lipid metabolism. Another portion is reduced by 5-alpha reductase to dihydrotestosterone (DHT), which is the more potent androgen at the prostate and hair follicle.

The cypionate ester increases lipophilicity and prolongs absorption from the intramuscular injection site. After injection, esterases gradually hydrolyze the ester, releasing free testosterone into the circulation. Peak levels occur within several days, then decline over the following one to two weeks. This pharmacology produces predictable but not perfectly steady levels, with mild peaks and troughs that some patients perceive as energy swings. Exogenous testosterone suppresses gonadotropin secretion, reducing endogenous testosterone production and spermatogenesis. This must be discussed with patients of reproductive age. The Endocrine Society provides guidance on diagnosing and treating male hypogonadism.

Clinical Use

Testosterone replacement is indicated in men with consistent symptoms of hypogonadism plus unequivocally low morning total testosterone confirmed on at least two occasions. Symptoms commonly include decreased libido, erectile dysfunction, fatigue, loss of muscle mass, increased body fat, depressed mood, hot flashes, gynecomastia, and reduced bone density. Causes include primary testicular failure (Klinefelter, prior orchitis, chemotherapy, trauma) and secondary causes (pituitary or hypothalamic disease, opioid use, severe systemic illness, obesity, and certain medications). Diagnosis must precede treatment; testosterone should not be given for symptoms alone or for normal age-related decline.

Within the testosterone class, alternatives include topical gels, transdermal patches, intranasal gel, buccal tablets, oral undecanoate, subcutaneous pellets, and other long-acting esters such as testosterone enanthate or undecanoate. The choice depends on patient preference, cost, comfort with injections, transfer risk to family members, and serum-level stability needs. Cypionate offers low cost and infrequent dosing but requires an injection. The American Urological Association and the Endocrine Society recommend baseline screening for prostate disease, sleep apnea, polycythemia, and cardiovascular risk before initiation. Patients with desire to preserve fertility should not start exogenous testosterone without first discussing alternatives such as clomiphene or human chorionic gonadotropin. Our men's health checklist reviews the broader screening framework.

How to Take It

Testosterone cypionate is supplied as 100 mg/mL and 200 mg/mL solutions in cottonseed or sesame oil. Typical dosing is 50 to 200 mg intramuscularly every one to two weeks, individualized to keep total testosterone in the mid-normal physiologic range. Some clinicians prefer subcutaneous administration with finer needles, which appears to provide similar pharmacokinetics with less injection-site discomfort. Common injection sites include the gluteal muscle, ventrogluteal area, lateral thigh, or deltoid for smaller volumes. Sites should be rotated. Patients comfortable with self-injection are taught sterile technique, needle disposal, and recognition of injection-site infection.

A missed dose should be administered as soon as remembered, then the schedule restarted from that date. Tablets and gels should not be substituted casually for an injectable regimen without physician guidance. During the first weeks patients may notice acne, oily skin, increased libido, mood improvement, mild fluid retention, and improved energy. Some men experience injection-day fatigue or mild flu-like symptoms. Storage at room temperature is appropriate; the medication should not be refrigerated, as cooling can cause the oil to thicken. Patients planning travel should arrange for safe transport in original containers with a copy of the prescription.

Monitoring and Follow-Up

Baseline labs include morning total testosterone (often paired with free or bioavailable testosterone), LH, FSH, prolactin in selected cases, complete blood count, lipid panel, liver enzymes, hemoglobin A1c, PSA in men over 40 or those at higher prostate cancer risk per shared-decision criteria, and assessment of obstructive sleep apnea symptoms. Cardiovascular risk should be evaluated. Follow-up labs at three to six months include morning total testosterone drawn at the trough, hematocrit, PSA, and lipid panel. Once stable, monitoring is repeated every 6 to 12 months.

Target testosterone is generally 400 to 700 ng/dL for trough levels, adjusted by symptom response and tolerability. A meaningful response includes improved energy, libido, mood, and erectile function within three to six months. Hematocrit above 54 percent should prompt dose reduction, increased dosing interval, or therapeutic phlebotomy because of the risk of thrombosis. PSA rising more than 1.4 ng/mL within 12 months or above 4 ng/mL warrants urology referral. Red numbers include unexplained chest pain or stroke symptoms, calf swelling or sudden dyspnea suggesting venous thromboembolism, hematocrit above 54, persistent severe acne, gynecomastia with mass or discharge, or abnormal liver enzymes. The American Heart Association notes ongoing study of cardiovascular safety of testosterone replacement and encourages individualized decisions in men with cardiovascular disease.

Special Populations

Elderly men can use testosterone replacement when hypogonadism is biochemically confirmed and symptomatic, but cardiovascular and prostate risks should be reviewed carefully. Renal and hepatic impairment generally do not preclude treatment but warrant cautious dosing. Severe liver disease is a relative contraindication. Patients with untreated severe sleep apnea, uncontrolled heart failure, hematocrit above 50 at baseline, or active prostate or breast cancer should not initiate therapy. Testosterone is contraindicated in pregnant women because of virilization risk to a female fetus; partners of pregnant women using transdermal forms should avoid skin-to-skin contact with treated areas, though this is less of an issue with injectables. The medication has no role in women for testosterone replacement and is not approved in pediatric patients except in very specific endocrine settings under specialty care. Patients with desire for future fertility should be counseled that exogenous testosterone reduces sperm production and may take many months to recover after discontinuation; alternatives such as clomiphene or hCG should be considered. As a Schedule III controlled substance, prescriptions require careful documentation and may be subject to state monitoring program requirements.

When to Contact Your Doctor

Call the office or seek emergency care promptly for chest pain, sudden shortness of breath, calf swelling, slurred speech, one-sided weakness, severe headache, or visual changes that could suggest a thrombotic event or stroke. New persistent erection lasting more than four hours requires emergency evaluation for priapism. Significant new acne, gynecomastia, mood changes, sleep disruption, or apnea episodes deserve assessment. Notify the office about new abdominal pain, jaundice, or significant fatigue, which could indicate hepatic effects. Discuss any plan to attempt conception in advance because adjustments are usually needed. Notify the office of pregnancy in a partner if topical formulations are involved.

Patients should be cautious about marketing claims for testosterone as an anti-aging or wellness intervention. Replacement is appropriate only when biochemically confirmed hypogonadism is accompanied by consistent symptoms; treating numbers alone or treating men with normal levels does not produce sustained benefit and exposes patients to avoidable risk. Lifestyle factors that influence endogenous testosterone include obesity, poor sleep, untreated obstructive sleep apnea, chronic alcohol use, and certain medications including chronic opioids and corticosteroids. Addressing these reversible factors first sometimes restores adequate testosterone without exogenous therapy. Patients should also recognize that responses to therapy take months, not weeks; expectations should be set accordingly. Adequate hydration during outdoor activity in our warm climate, especially when hematocrit may rise on therapy, helps reduce thrombotic risk. Coordination with the primary care clinician on cardiovascular risk reduction, cancer screening, and mental health remains essential during long-term treatment.

If you have symptoms of low testosterone confirmed by morning labs, our internal medicine team can help evaluate causes and discuss whether replacement therapy is appropriate. Contact us or schedule a visit for a thorough evaluation.