Hypogonadism is a condition in which the body doesn’t produce enough sex hormones, primarily testosterone in men and estrogen in women. It’s surprisingly common: in a large U.S. study of men 45 and older visiting primary care offices, nearly 39% had testosterone levels below the diagnostic threshold. The condition affects energy, sexual function, fertility, bone strength, and mood, and it becomes more likely with age, with the risk increasing about 17% for every additional decade of life.
How the Hormone System Works (and Breaks Down)
Sex hormone production depends on a signaling chain that starts in the brain. The hypothalamus sends a signal to the pituitary gland, which then releases hormones that tell the gonads (testes or ovaries) to produce testosterone or estrogen. A problem at any point along this chain can cause hypogonadism, and where the problem occurs determines which type you have.
In primary hypogonadism, the gonads themselves are damaged or dysfunctional. Despite strong signals from the brain telling them to produce hormones, they can’t keep up. Because the pituitary keeps ramping up its signals in response, blood tests will show high levels of stimulating hormones alongside low sex hormones.
In secondary hypogonadism, the gonads are perfectly healthy but aren’t receiving adequate signals from the brain. The pituitary gland or hypothalamus isn’t doing its job, so the gonads simply sit idle. Blood tests in this case show low stimulating hormones along with low sex hormones. This distinction matters because it shapes which treatments will work.
Common Causes
Primary hypogonadism can result from genetic conditions like Klinefelter syndrome in men or Turner syndrome in women, where chromosomal differences impair gonad development. Physical damage from injury, surgery, infection, or radiation to the testes or ovaries also falls into this category. In women, premature ovarian failure (ovarian function declining before age 40) is a well-recognized cause.
Secondary hypogonadism has a broader range of triggers. Pituitary tumors are a classic cause, but so are head injuries, pituitary surgery, and brain radiation. Certain medications are common culprits: opioid painkillers, anabolic steroids, and some hormonal treatments can suppress the brain’s signaling to the gonads. Chronic alcohol use, extreme exercise, severe obesity, and systemic diseases like iron overload (hemochromatosis) or sarcoidosis can also shut down the signaling chain. A genetic form called Kallmann syndrome causes secondary hypogonadism from birth and is associated with an absent or reduced sense of smell.
Symptoms in Men
The symptoms depend on when hypogonadism develops. If it begins before puberty, the body never receives the hormonal cues needed for typical male development. The result can include underdeveloped genitalia, breast tissue growth, and arms and legs that grow disproportionately long compared to the torso.
When it develops after puberty, the changes are more gradual and easy to dismiss as normal aging. Low sex drive, erectile dysfunction, and reduced energy are the hallmarks. Many men also notice decreased muscle mass, increased body fat, thinning facial and body hair, difficulty concentrating, and depressed mood. Hot flashes can occur, and over time, bone density drops, raising the risk of fractures. Infertility is another significant consequence, since testosterone is essential for sperm production.
Symptoms in Women
In women, hypogonadism primarily manifests as disruptions to the menstrual cycle. Before puberty, it can delay or prevent the onset of menstruation entirely. After puberty, it typically presents as missed periods (amenorrhea), irregular periods, hot flashes, and vaginal dryness from estrogen deficiency. Some women also experience low libido, fatigue, and loss of bone density. In cases involving excess androgen production from related conditions, symptoms like excess facial hair growth, hair thinning on the scalp, and voice deepening can occur.
How It’s Diagnosed
Diagnosis starts with a blood test measuring total testosterone (in men) or estrogen and related hormones (in women). For men, the most widely used threshold is a total testosterone level below 300 ng/dL, which is the cutoff recommended by the American Urological Association. The Endocrine Society sets a slightly lower boundary at 264 ng/dL for healthy, non-obese young men, while European guidelines use 350 ng/dL. These differences reflect ongoing debate about where “low” truly begins, especially since symptoms don’t always correlate neatly with a specific number.
Testosterone levels in men peak in the early morning and decline through the day, so blood draws are typically scheduled before 10 a.m. Fasting was traditionally recommended, though recent evidence suggests that eating before the test may not significantly alter results. At least two separate low readings on different days are generally required before a diagnosis is made, because testosterone fluctuates naturally. Additional blood work measuring pituitary hormones helps determine whether the cause is primary or secondary.
Testosterone Replacement Therapy
For men with confirmed hypogonadism who aren’t trying to conceive, testosterone replacement is the standard treatment. Several delivery methods exist, each with different schedules and trade-offs:
- Topical gels are applied daily to the shoulders, upper arms, abdomen, or thighs. They maintain relatively steady hormone levels but require careful skin-to-skin contact precautions to avoid transferring testosterone to others.
- Injections are given on a schedule ranging from weekly to every few weeks, depending on the formulation. Levels can swing between peaks and valleys between doses.
- Transdermal patches are applied nightly and provide a steady release, though skin irritation is common.
- Subdermal pellets are implanted under the skin every three to six months, offering the longest-lasting option with the least day-to-day maintenance.
- Nasal gels and buccal tablets are applied multiple times per day (three times and twice daily, respectively) and avoid skin transfer concerns.
Testosterone replacement is not appropriate for everyone. It is contraindicated in men with untreated prostate cancer or breast cancer, and extra caution applies for men at elevated prostate cancer risk, including those with a first-degree relative who had prostate cancer and African American men with elevated PSA levels.
Fertility Considerations
This is one of the most important things to understand about hypogonadism treatment: testosterone replacement therapy can make you infertile. Adding external testosterone signals the brain that hormone levels are adequate, which shuts down the pituitary’s stimulation of the testes. Without that stimulation, sperm production drops dramatically and can cease entirely, a condition called azoospermia.
For men who want to preserve or restore fertility, the approach is different. Instead of testosterone, doctors can prescribe medications that stimulate the body’s own hormone production. Human chorionic gonadotropin (hCG) mimics the pituitary’s signal to the testes, boosting both testosterone and sperm production simultaneously. It’s often paired with medications like clomiphene citrate, which enhances the pituitary’s output of stimulating hormones. In men who became infertile from testosterone use, this combination successfully reversed azoospermia in nearly all cases in clinical experience, though recovery took four to six months.
If you’re a man diagnosed with hypogonadism and you think you might want children in the future, make sure fertility is part of the treatment conversation before starting any therapy.
Treatment for Women
In women, treatment focuses on replacing the deficient hormones, most commonly estrogen. Hormone replacement can restore menstrual cycles, relieve hot flashes and vaginal dryness, and protect bone density. For women with premature ovarian failure who wish to conceive, fertility treatments involving hormone stimulation may be an option, though the approach varies significantly depending on the underlying cause. The treatment landscape for female hypogonadism is more individualized, since the condition intersects with reproductive planning, menopause management, and bone health in ways that differ for each person.