Hypogonadism means your body’s sex glands produce little or no sex hormones. In men, those glands are the testes (producing testosterone). In women, they’re the ovaries (producing estrogen and progesterone). The condition can start before birth, during puberty, or later in adulthood, and the effects depend heavily on when it begins.
How the Hormonal System Works
Sex hormone production isn’t just about the gonads themselves. It’s controlled by a signaling chain that starts in the brain. The hypothalamus, a small region at the base of the brain, sends a hormone signal to the pituitary gland. The pituitary then releases two messenger hormones that tell the testes or ovaries to produce testosterone or estrogen. If any link in this chain breaks down, hormone levels drop.
This distinction matters because it determines what type of hypogonadism you have, and that shapes how it’s treated.
Primary vs. Secondary Hypogonadism
Primary hypogonadism means the gonads themselves are the problem. The brain is sending the right signals, but the testes or ovaries can’t respond properly. Blood tests in this form show low sex hormones but high levels of the pituitary’s messenger hormones (LH and FSH), because the brain keeps trying harder to get a response that never comes.
Common causes of primary hypogonadism include genetic conditions like Klinefelter syndrome (the most common genetic cause in men) and Turner syndrome in women, undescended testes, and damage from chemotherapy or radiation therapy. Injury, infection, or autoimmune disease affecting the gonads can also be responsible.
Secondary hypogonadism (sometimes called central hypogonadism) means the problem is in the brain, specifically the hypothalamus or pituitary gland. The gonads could work fine if they received the right signals, but they don’t. Blood tests here show low sex hormones along with low or low-normal LH and FSH. Causes include pituitary tumors, Kallmann syndrome (a congenital condition affecting the hypothalamus), head injuries, obesity, and long-term opioid use. Intracranial tumors can also compress the connection between the hypothalamus and pituitary, disrupting communication.
This blood test pattern is exactly how doctors distinguish the two types. Elevated LH and FSH point to the gonads. Low or normal LH and FSH with low testosterone point to the brain.
Symptoms in Men
What hypogonadism looks like depends on when it starts. If it begins before or during puberty, it can delay or prevent normal development: limited muscle growth, lack of voice deepening, and absent or sparse facial and body hair.
In adult men, the symptoms tend to creep in gradually. Early signs include low sex drive, reduced energy, and depression. Over time, the effects become more visible: difficulty getting or maintaining erections, loss of muscle mass, less body and facial hair, and growth of breast tissue. Some men also develop trouble concentrating and emotional changes that resemble menopause symptoms. Because these changes happen slowly, many men attribute them to aging or stress rather than a hormonal condition.
Symptoms in Women
In women, hypogonadism typically shows up as missed or absent menstrual periods, hot flashes, vaginal dryness, and reduced sex drive. Infertility is a common consequence, since ovulation depends on the same hormonal signals that are disrupted. When the condition begins before puberty, breast development and menstruation may not start on their own. Hypogonadotropic hypogonadism (the secondary type) accounts for roughly 10% of ovulation disorders in women.
How It’s Diagnosed
Diagnosis starts with a blood test measuring total testosterone (in men) or estrogen (in women), drawn in the morning when hormone levels are highest. For men, the commonly used threshold for low testosterone is 300 ng/dL, recommended by the American Urological Association. But this number is debated. Other professional organizations use cutoffs ranging from 200 to 350 ng/dL, and recent research suggests that age-specific values may be more accurate. For men in their early 20s, the 33rd percentile (below which levels are considered low) is around 409 ng/dL, while for men aged 40 to 44 it drops to about 350 ng/dL.
If initial tests confirm low hormones, the next step is measuring LH and FSH to determine whether the problem is primary or secondary. Additional testing may follow depending on suspected causes, such as genetic testing for Klinefelter or Turner syndrome, or brain imaging to check for pituitary tumors.
Treatment Options
Treatment centers on replacing the missing hormones. For men, testosterone replacement comes in several forms: gels applied daily to the upper arm, shoulder, or thigh (the body absorbs it through the skin), injections given on a regular schedule, skin patches, and pellets surgically implanted under the skin every three to six months. The choice often comes down to lifestyle preferences and how steady you want your hormone levels to be. Gels provide a consistent daily dose but require care to avoid skin-to-skin transfer to others. Injections are less frequent but can cause hormone levels to spike and dip between doses.
For women, treatment typically involves estrogen and progesterone replacement to restore menstrual cycles, relieve symptoms like hot flashes and vaginal dryness, and protect bone health. If fertility is the goal, treatment takes a different path, focusing on stimulating the ovaries directly rather than simply replacing hormones.
Long-term Risks of Untreated Hypogonadism
Left untreated, hypogonadism does more than cause uncomfortable symptoms. Bone loss is one of the most serious consequences. Testosterone and estrogen both play a critical role in maintaining bone density, and prolonged deficiency leads to osteoporosis and a significantly higher fracture risk. When hypogonadism starts during puberty and goes untreated, peak bone mass (the strongest your bones will ever be) is severely affected. In one documented case of a man with four decades of untreated hypogonadism, imaging revealed multiple spinal fractures and bone density scores well below normal.
Cardiovascular risk also rises. Long-term testosterone deficiency in men is associated with elevated cholesterol, impaired blood sugar regulation, and increased risk of heart disease. The same case showed the development of ischemic heart disease after years without treatment. Male osteoporosis and cardiac complications from hypogonadism are often underdiagnosed because clinicians don’t always connect these problems to a hormonal cause, particularly in younger men who wouldn’t typically be screened for them.