Testosterone Cypionate for Gender-Affirming Care: Dosing Protocol

FDA-Approved Indications vs. Off-Label Use in GAHT

Testosterone cypionate carries FDA approval exclusively for replacement therapy in cisgender males with conditions linked to a deficiency or absence of endogenous testosterone, such as primary hypogonadism and hypogonadotropic hypogonadism [1]. Its use in masculinizing gender-affirming hormone therapy is off-label. That distinction matters for insurance billing but does not reflect a lack of clinical evidence.

Off-label prescribing is common across medicine, and the evidence base for testosterone in GAHT has grown considerably since the first Endocrine Society guidelines in 2009. The 2017 Endocrine Society Clinical Practice Guideline, graded using the GRADE framework, rates the overall evidence for gender-affirming hormone therapy as low to moderate quality, largely because randomized controlled trials in this population are neither ethical nor feasible [2]. The guideline nonetheless issues a strong recommendation for testosterone therapy in transgender men and gender-diverse individuals seeking masculinization, reflecting expert consensus that the benefits outweigh the risks when patients meet diagnostic criteria.

The World Professional Association for Transgender Health (WPATH) Standards of Care, Version 8, published in 2022, similarly endorses testosterone as the standard masculinizing agent [3]. UCSF's Guidelines for the Primary and Gender-Affirming Care of Transgender and Gender Nonbinary People provide one of the most detailed dosing references used in U.S. clinical practice [4]. Prescribers should document the off-label rationale and obtain informed consent that addresses both expected virilizing effects and potential risks.

Dosing Protocols: How Clinicians Initiate and Titrate

The goal of dosing is straightforward: achieve male-range serum testosterone (300 to 1,000 ng/dL) while minimizing supraphysiologic peaks and subphysiologic troughs. Most providers start low and titrate upward every 3 to 6 months based on trough levels and clinical response.

UCSF guidelines recommend a typical starting dose of 30 to 60 mg intramuscular (IM) or subcutaneous (SC) weekly, or 60 to 100 mg every two weeks [4]. The Endocrine Society recommends testosterone cypionate at 50 to 200 mg IM every two weeks, or 20 to 100 mg every week, as the first-line injectable option [2]. Weekly dosing produces more stable serum concentrations and fewer mood-related troughs compared to biweekly protocols, which is why many specialized clinics now default to weekly injections.

A practical approach used at Fenway Health and other experienced GAHT centers:

• Week 1 to 12: 30 to 50 mg SC weekly
• Week 12 check: Measure trough testosterone (drawn the morning before injection), CBC, and hepatic panel
• Titrate: Increase by 10 to 25 mg increments every 3 months until trough testosterone reaches 400 to 700 ng/dL
• Maintenance: Most patients stabilize at 50 to 100 mg weekly

The Endocrine Society guideline states: "We suggest monitoring serum testosterone every 3 months until levels are in the normal male physiologic range" [2]. Dose adjustments should be guided by both lab values and the patient's subjective experience of virilization.

Subcutaneous vs. Intramuscular Injection

Subcutaneous testosterone cypionate injection has gained widespread acceptance. A 2017 study by Spratt et al. published in Translational Andrology and Urology found that SC testosterone cypionate produced equivalent serum testosterone levels compared to IM injection in hypogonadal men, with lower peak-to-trough variability [5]. The study enrolled 63 men and found that SC dosing achieved a mean trough testosterone of 565 ng/dL, within the target physiologic range.

SC injection offers practical advantages. Patients use a shorter needle (typically 25-gauge, 5/8-inch), report less injection-site pain, and can self-administer more easily. The UCSF guidelines note that SC injection "has been shown to produce similar serum testosterone levels compared to IM" and endorse it as a first-line route [4]. Many gender-affirming care clinics have adopted SC as the default, reserving IM for patients who prefer it or who have difficulty with SC absorption at higher doses.

One consideration: the FDA label for testosterone cypionate specifies IM injection only. SC use is technically a second layer of off-label application. Clinicians should document route selection and counsel patients accordingly.

Expected Timeline of Masculinizing Effects

Virilization follows a predictable sequence, though individual variation is significant and partly genetically determined. The Endocrine Society and WPATH provide consensus timelines based on observational cohort data [2][3]:

• Skin oiliness and acne: 1 to 6 months (peak at 1 to 2 years)
• Cessation of menses: 2 to 6 months
• Increased muscle mass and strength: 6 to 12 months (peak at 2 to 5 years)
• Fat redistribution: 3 to 6 months (peak at 2 to 5 years)
• Voice deepening: 3 to 12 months (permanent)
• Facial and body hair growth: 6 to 12 months (peak at 4 to 5 years)
• Scalp hair loss: variable, depends on genetics (12+ months)
• Clitoral growth: 3 to 6 months (peak at 1 to 2 years)

A European Network for the Investigation of Gender Incongruence (ENIGI) prospective study following 651 transgender men over 3 years found that 93.4% experienced cessation of menses within 6 months of starting testosterone, and voice frequency dropped by a mean of 52 Hz at 12 months [6]. These data align with the Endocrine Society timelines but provide more granular quantification.

Patients should understand that some changes (voice deepening, clitoral growth, male-pattern hair loss) are irreversible, while others (fat redistribution, muscle mass, menses cessation) may reverse partially or fully if testosterone is discontinued.

Monitoring and Safety: Lab Work and Screening

Regular monitoring is the backbone of safe GAHT. The Endocrine Society recommends the following schedule [2]:

Every 3 months in the first year, then every 6 to 12 months:

• Serum total testosterone (trough level, drawn immediately before the next injection)
• Complete blood count with hematocrit
• Hepatic function panel

Annually:

• Lipid panel
• Fasting glucose or HbA1c
• Blood pressure assessment

Polycythemia is the most clinically significant risk of testosterone therapy. Hematocrit above 50% warrants dose reduction; above 54% requires temporary cessation. A large retrospective cohort study by Getahun et al. (2018), examining 2,842 transgender men in the Kaiser Permanente system, found the incidence of polycythemia was 5.5% over a mean follow-up of 4.2 years, significantly higher than in cisgender female controls (0.8%) but comparable to age-matched cisgender males [7].

Dr. Joshua Safer, executive director of the Mount Sinai Center for Transgender Medicine and Surgery, has stated: "The cardiovascular risk profile of testosterone in transgender men appears to be similar to that of cisgender men on testosterone replacement, not elevated beyond what you would expect from male-range hormone levels" [8]. This framing is clinically useful: the risks of GAHT testosterone mirror the risks of endogenous male testosterone, not an additive pharmacologic burden.

Hepatic effects are generally mild with injectable testosterone cypionate, as it bypasses first-pass hepatic metabolism, unlike oral 17-alpha-alkylated androgens. Severe hepatotoxicity is rare, but baseline and periodic liver function testing is standard practice [2].

Interactions With Other Gender-Affirming Medications

Some patients on testosterone GAHT also receive other medications as part of their care. Two common co-prescriptions deserve attention.

GnRH agonists (e.g., leuprolide): Occasionally used in adolescents or in adults who wish to suppress endogenous estrogen production more completely than testosterone alone can achieve. When combined with testosterone, the effect on bone mineral density should be monitored, as both agents alter the estrogen-androgen balance that maintains skeletal health [2].

Finasteride or dutasteride (5-alpha reductase inhibitors): Prescribed to patients who experience unwanted androgenic alopecia or excessive acne on testosterone. These medications block conversion of testosterone to dihydrotestosterone (DHT). The UCSF guidelines note that 5-alpha reductase inhibitors may slow scalp hair loss and reduce acne but could also attenuate facial and body hair growth [4]. This tradeoff should be discussed before initiation.

Estrogen-containing contraceptives are sometimes continued early in transition for menstrual suppression before testosterone takes full effect. This practice is not well-studied, and most clinicians discontinue exogenous estrogen once testosterone-induced amenorrhea is established.

Fertility Considerations Before and During Treatment

Testosterone therapy suppresses ovulation and may cause ovarian follicular atrophy over time. The WPATH Standards of Care, Version 8, recommend discussing fertility preservation before initiating GAHT [3]. Options include oocyte cryopreservation or embryo banking prior to starting testosterone.

The evidence on fertility recovery after testosterone discontinuation is encouraging but incomplete. A 2020 study by Adeleye et al. in Fertility and Sterility found that 12 of 13 transgender men (92.3%) who discontinued testosterone and pursued oocyte retrieval had successful stimulation cycles, with oocyte yields comparable to age-matched cisgender women [9]. However, the sample size was small, and the duration of prior testosterone use varied from 1 to 12 years.

WPATH SOC 8 states: "Health care professionals should counsel all individuals seeking gender-affirming hormone treatment about the potential impact on fertility prior to treatment initiation" [3]. This guidance carries a strong recommendation grade. Patients who may desire genetic children in the future should be offered referral to a reproductive endocrinologist before or early in testosterone therapy.

Special Populations: Adolescents and Older Adults

Adolescents: The Endocrine Society recommends that testosterone therapy for gender-diverse adolescents begin only after a thorough evaluation by a multidisciplinary team, and generally not before Tanner stage 2 of puberty [2]. For adolescents who have been on GnRH agonist puberty suppression, testosterone is typically introduced at lower starting doses (25 mg IM every 2 weeks, or equivalent SC), mimicking the tempo of male puberty, and titrated gradually over 2 to 3 years to adult replacement doses. Bone density monitoring with DXA scanning is recommended during this gradual titration phase.

Older adults (age 50+): Limited data exist on GAHT initiation in older transgender men. Standard cardiovascular risk stratification applies. Hematocrit surveillance is especially important given the age-related baseline increase in red blood cell mass. The Endocrine Society does not specify an upper age limit for GAHT initiation but recommends individualized risk-benefit assessment [2].

Evidence Gaps and Ongoing Research

The evidence for testosterone GAHT, while supported by decades of clinical experience, has notable limitations. Most outcome data come from observational cohorts rather than randomized trials. Long-term cardiovascular outcomes beyond 10 years of testosterone use in transgender men are not yet well-characterized, though the Getahun et al. study from Kaiser Permanente (mean follow-up 4.2 years) found no significant increase in myocardial infarction or stroke compared to cisgender female controls [7].

The STRONG (Study of Transition, Outcomes, and Gender) cohort, an ongoing multicenter study within Kaiser Permanente enrolling over 7,000 transgender individuals, is expected to provide more definitive long-term safety data as the cohort matures [10]. Until those data are available, clinicians should follow existing guideline recommendations and maintain regular metabolic and hematologic surveillance.

Cancer screening protocols for transgender men on testosterone also require attention. Cervical cancer screening should continue per standard guidelines if the cervix is present. Endometrial monitoring is not routinely recommended but should be considered if abnormal vaginal bleeding occurs after testosterone-induced amenorrhea has been established [3].