Hypogonadism is a condition in which the body produces insufficient sex hormones, primarily testosterone in men and estrogen in women. It can develop at any age, from birth through late adulthood, and affects sexual function, energy, fertility, bone strength, and body composition. The condition falls into two distinct categories depending on where the problem originates, and understanding the difference matters because it shapes both diagnosis and treatment.
How the Hormone System Works
Your sex hormones are regulated by a chain of signals that runs from the brain to the gonads (testes or ovaries). The hypothalamus, a small region at the base of the brain, releases a signaling hormone called GnRH in rhythmic pulses. Those pulses tell the pituitary gland to produce two hormones, LH and FSH, which travel through the bloodstream to the gonads. LH stimulates the gonads to produce testosterone or estrogen, while FSH supports sperm production in men and egg development in women.
This chain works as a feedback loop. When sex hormone levels rise high enough, the brain dials back its signals. When levels drop, the brain ramps them up. Hypogonadism occurs when something breaks this loop, either at the level of the gonads themselves or higher up in the brain.
Primary vs. Secondary Hypogonadism
Primary hypogonadism originates in the gonads. The testes or ovaries are damaged or dysfunctional, so they can’t produce enough hormones even though the brain is sending normal (or even amplified) signals. Because the brain detects low hormone levels and tries to compensate, LH and FSH levels are typically elevated. This pattern is sometimes called hypergonadotropic hypogonadism.
Secondary hypogonadism originates in the hypothalamus or pituitary gland. The gonads themselves are capable of working, but they aren’t receiving adequate signals. In this case, testosterone or estrogen is low, and LH and FSH are also low or inappropriately normal. This pattern is called hypogonadotropic hypogonadism.
The distinction is clinically important. Someone with secondary hypogonadism may be able to restore fertility with treatments that stimulate the brain’s signaling pathway, while someone with primary gonadal failure typically cannot.
Common Causes
Primary Hypogonadism
The most common congenital cause of primary hypogonadism in men is Klinefelter syndrome, a genetic condition affecting roughly 1 in 1,000 male births. Men with Klinefelter syndrome carry an extra X chromosome, which leads to small, firm testes, tall stature, and reduced testosterone production. In women, Turner syndrome (a missing or partially missing X chromosome) is the analogous genetic cause.
Acquired causes of primary hypogonadism include autoimmune damage to the gonads, chemotherapy or radiation therapy, surgical removal of the testes or ovaries, and infections such as mumps orchitis in men.
Secondary Hypogonadism
Kallmann syndrome is one of the best-known congenital causes. It results from a genetic mutation that prevents GnRH-producing neurons from migrating to the correct location in the brain during fetal development. People with Kallmann syndrome also lack a sense of smell, because the same migration pathway affects olfactory neurons.
Acquired secondary hypogonadism has a wider range of triggers. Pituitary tumors can compress or destroy hormone-producing cells. Head trauma and brain radiation can damage the hypothalamus. High prolactin levels, whether from a tumor or medications, directly suppress GnRH pulsing. In women, functional hypothalamic amenorrhea, often driven by extreme stress, excessive exercise, or very low body weight, reduces GnRH output enough to shut down ovulation and menstrual cycles. Obesity is another significant contributor: excess body fat disrupts hormonal signaling through multiple pathways, including altered leptin signaling and increased conversion of testosterone to estrogen in fat tissue.
Symptoms in Men
The earliest signs tend to be reduced sex drive, lower energy, and depressed mood. These are easy to attribute to stress or aging, which is one reason hypogonadism often goes undiagnosed for years. More specific symptoms include fewer spontaneous and morning erections, difficulty achieving or maintaining erections, and reduced testicular size.
Over time, low testosterone leads to loss of muscle mass, increased body fat (particularly around the midsection), decreased facial and body hair growth, and breast tissue enlargement. Bone density declines, raising fracture risk. Fertility is also affected: testosterone is essential for sperm production, so men with hypogonadism often have low sperm counts.
When hypogonadism develops before or during puberty, the effects are more pronounced. Boys may not develop typical secondary sex characteristics, including deepening of the voice, growth of facial hair, and genital development.
Symptoms in Women
In women, hypogonadism disrupts the menstrual cycle. Periods may become irregular, infrequent, or stop entirely. If the condition begins before puberty, breast development may be delayed or absent, and menstruation may never start. In adult women, the most common complaints are loss of periods, difficulty conceiving, vaginal dryness, hot flashes, and reduced libido.
Low estrogen has serious long-term consequences for bone health. Women with untreated hypogonadism face significantly higher rates of osteoporosis and fractures later in life. Early menopause, whether natural or caused by gonadal failure, accelerates this bone loss.
How It’s Diagnosed
Diagnosis starts with a blood test measuring total testosterone (in men) or estradiol (in women). For men, the Endocrine Society’s harmonized reference range for testosterone is 264 to 916 ng/dL, based on data from non-obese men aged 19 to 39. Levels consistently below 264 ng/dL, confirmed on at least two separate tests, point toward hypogonadism.
Timing matters for accuracy. Testosterone peaks in the early morning, so blood draws are typically scheduled between 7 and 10 a.m. You may need to fast for several hours beforehand, and certain medications can affect results, so let your provider know what you’re taking.
Once low hormone levels are confirmed, the next step is measuring LH and FSH. Elevated LH and FSH with low testosterone indicate primary hypogonadism: the brain is working overtime to stimulate gonads that can’t keep up. Low or normal LH and FSH alongside low testosterone point to secondary hypogonadism: the brain isn’t sending adequate signals. This distinction guides everything that follows, from additional imaging (an MRI of the pituitary, for instance) to treatment options.
Treatment Options
The goal of treatment is to restore sex hormone levels to a normal range, relieving symptoms and protecting against long-term complications like bone loss. The approach depends on whether fertility is a priority.
Hormone Replacement
For men, testosterone can be delivered through several methods. Transdermal options, including gels, creams, sprays, and patches, are generally preferred because they mimic the body’s natural daily rhythm of hormone release. Patches are popular for convenience, usually applied once or twice per week. Gels and creams are applied daily but can have absorption variability, sometimes not delivering the full prescribed dose. Injectable testosterone is another option, given on a schedule that ranges from weekly to every few months depending on the formulation. Pellet therapy involves implanting small hormone pellets under the skin near the lower back, providing steady release over several months.
For women, estrogen replacement (often combined with progesterone for those with a uterus) addresses symptoms and protects bone density. Delivery methods include pills, patches, creams, and gels, with patches being a commonly recommended starting point.
Fertility Considerations
Testosterone replacement in men suppresses sperm production and can shrink the testes. For men who want to have children, this is a critical consideration. In cases of secondary hypogonadism, treatments that stimulate the body’s own hormone production (rather than replacing it from outside) can improve both testosterone levels and sperm count simultaneously.
Risks of Testosterone Therapy
Testosterone replacement carries specific risks that require monitoring. It can stimulate excessive red blood cell production, thickening the blood and increasing the risk of clots. A clot that breaks free can travel to the lungs, causing a pulmonary embolism. Regular blood count monitoring helps catch this early.
Testosterone therapy can also worsen sleep apnea, a condition in which breathing repeatedly stops during sleep. If you already have sleep apnea or are at high risk for it, this needs to be factored into treatment decisions. And as noted above, testosterone therapy limits sperm production, which is effectively a form of male contraception, though not a reliable one.
These risks don’t mean treatment should be avoided when it’s genuinely needed. They mean that ongoing follow-up with blood work and symptom tracking is part of the process, not a one-time prescription.