Testosterone is a powerful hormone known as an androgen that plays a significant role in the development of secondary sex characteristics. When administered as a medication, a primary goal for many individuals is the induction of amenorrhea, the complete cessation of the menstrual cycle. This therapy introduces supraphysiologic levels of testosterone into the bloodstream, fundamentally altering the body’s hormonal environment. The resulting shift in hormone balance actively works to stop the cyclical process of menstruation. This effect is a predictable consequence of consistent testosterone use.
How Testosterone Affects the Menstrual Cycle
The mechanism by which administered testosterone halts menstruation involves suppressing the Hypothalamic-Pituitary-Gonadal (HPG) axis, the central regulator of the reproductive system. The hypothalamus normally secretes gonadotropin-releasing hormone (GnRH), which signals the pituitary gland to release Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH). These gonadotropins stimulate the ovaries, promoting follicular development and the cyclical production of estrogen and progesterone.
High levels of testosterone act as a strong negative feedback signal, targeting the hypothalamus and pituitary gland. This signal dramatically reduces the output of LH and FSH. Without sufficient levels of these hormones, the ovaries become functionally suppressed, preventing ovulation and the normal cyclical rise and fall of estrogen and progesterone. Since the menstrual cycle relies on the proliferation and subsequent shedding of the uterine lining controlled by these hormones, suppression prevents the lining from building up, and menstruation ceases. This suppressive effect is dependent on achieving and maintaining a therapeutic dose.
The Typical Timeline for Menstruation Cessation
The time it takes for menstruation to stop completely after starting testosterone therapy is variable, but a predictable timeline exists for most individuals. Cessation of menses, or amenorrhea, typically occurs within three to six months of beginning consistent treatment. Studies show that approximately 75% of individuals achieve full menstrual suppression within this six-month window.
Before full cessation, many people experience a gradual change, with periods becoming lighter, shorter, or less frequent. The specific type of testosterone formulation used can influence the timing, as injectable forms may lead to suppression more quickly than topical gels. Individual physiology, genetics, and the precise dosage contribute to how quickly the body responds to the hormonal changes. While most stop within six months, a small percentage may take longer than a year to achieve complete cessation.
Related Physical Changes Caused by Testosterone
Testosterone is an androgen, and its effects on the body cause a cascade of changes collectively known as virilization. One noticeable change is the deepening of the voice, resulting from the thickening of the vocal cords. This change is permanent and often begins within the first few months of therapy.
The hormone also stimulates the growth of terminal hair, leading to increased body and facial hair (hirsutism). Skin quality often changes, becoming thicker and oilier, which frequently leads to the onset or worsening of acne.
Testosterone therapy significantly alters body composition by increasing muscle mass and promoting fat redistribution away from the hips and thighs. This often leads to a more angular appearance. Furthermore, the external genitalia may experience growth and enlargement, which is an expected physical change resulting from the hormone’s direct action.
Medical Monitoring and Addressing Irregular Bleeding
Medical monitoring is necessary during testosterone therapy to ensure safety and confirm hormone levels are within the desired therapeutic range. Regular blood work checks serum testosterone and estradiol levels, red blood cell count, and liver function. These checks help the prescribing clinician adjust the dosage to maximize effectiveness while minimizing potential health risks.
Irregular or breakthrough bleeding (spotting that occurs after the expected six-month cessation period) requires prompt medical investigation. The initial step is often checking hormone levels, as insufficient testosterone can fail to fully suppress the cycle. If the testosterone dose is confirmed to be in the physiological male range and bleeding persists, clinicians will rule out other gynecological issues.
Testosterone is not a reliable form of contraception, and the possibility of pregnancy must be considered when irregular bleeding occurs in sexually active individuals. If breakthrough bleeding continues despite optimized testosterone levels, the clinician may consider adding a progestin medication to aid in achieving full menstrual suppression. Persistent unsuppressed cycles on testosterone can theoretically carry a risk of endometrial overgrowth due to the unopposed action of estrogen.