Late-Onset Hypogonadism (LOH) is a clinical syndrome characterized by a deficiency in the production of the hormone testosterone, occurring in association with advancing age in men. LOH is distinct from congenital hypogonadism, which results from genetic conditions or damage that causes low testosterone from birth or early development. The diagnosis of LOH requires both the presence of certain symptoms and consistently low blood testosterone levels.
Identifying the Signs of Low Testosterone
The initial signs of reduced testosterone often appear gradually, making them difficult to distinguish from the normal aging process. Symptoms are generally grouped into three main categories: sexual, physical, and psychological or cognitive changes. Recognizing these patterns of change can prompt a medical consultation.
Sexual symptoms are often the most recognized indicators of a potential testosterone deficiency. These can include a noticeable decrease in libido or sexual desire. Men may also experience erectile dysfunction and a reduction in the frequency of spontaneous erections, particularly morning erections.
Physical changes often manifest as alterations in body composition and energy levels. Patients frequently report persistent fatigue or a lack of energy, which is not relieved by rest. Physical indications include:
- Decreased muscle mass and strength, coupled with an increase in body fat.
- Decreased bone density.
- Hot flashes.
- Loss of body hair.
Psychological and cognitive symptoms reflect the hormone’s influence on brain function and mood regulation. Men with low testosterone may experience several cognitive and mood changes:
- Mood disturbances, such as increased irritability or depressive feelings.
- Difficulty with concentration.
- Impaired memory.
- A general feeling of low motivation or drive.
Confirming the Diagnosis
The presence of suggestive symptoms alone is insufficient for an LOH diagnosis, requiring confirmation through specific laboratory testing. The diagnostic process focuses on measuring the amount of total testosterone circulating in the bloodstream. Medical guidelines suggest that blood samples must be collected in the morning, typically between 8 a.m. and 10 a.m., because testosterone levels naturally peak during this time of day.
A single low value is not definitive, and most medical protocols require two separate morning measurements on different days to confirm a persistent deficiency. An acute illness can temporarily suppress testosterone production, so the test must be performed while the patient is in a state of good general health. The established threshold for diagnosis varies slightly across guidelines, but a total testosterone level below approximately 300 nanograms per deciliter (ng/dL) is generally considered low enough to warrant further evaluation.
In certain situations, measuring free or bioavailable testosterone is also necessary to gain a more complete picture. Free testosterone is the portion of the hormone not bound to proteins, making it immediately available for use by the body’s tissues. This measurement is particularly relevant for men with conditions like obesity or diabetes, where protein levels can skew the total testosterone result, even when the active hormone level is low. Levels below about 65 picograms per milliliter (pg/mL) can provide supportive evidence for a diagnosis of LOH.
Medical Management of Late-Onset Hypogonadism
The standard treatment for confirmed Late-Onset Hypogonadism is Testosterone Replacement Therapy (TRT). This therapy is available in several formulations, allowing patients and physicians to select a method that best suits their lifestyle and preference. The goal of TRT is to maintain a consistent hormone level to alleviate symptoms associated with the deficiency.
Intramuscular injections are one of the most common and cost-effective delivery methods, administered into a large muscle like the glute or thigh. These injections are typically scheduled weekly or bi-weekly, but they can cause a peak in testosterone shortly after administration, followed by a trough right before the next dose. This fluctuation in hormone levels can sometimes lead to a temporary return of symptoms towards the end of the dosing interval.
Transdermal methods, such as topical gels and patches, offer a more consistent daily delivery of the hormone. Gels are applied once a day to the skin of the shoulders, upper arms, or abdomen. Patches are applied daily to the skin, providing a steady release that more closely mimics the body’s natural hormonal rhythm. A drawback of topical applications is the risk of accidental transfer to partners or children through skin-to-skin contact.
Another long-acting option is the subdermal pellet, where small, rice-sized pellets are inserted under the skin. These pellets dissolve slowly, continuously releasing a steady dose of testosterone over a period of three to six months. While this method is highly convenient and avoids the daily routine of gels or the peaks and troughs of injections, dosage adjustments are less flexible once the pellets have been implanted.
Understanding the Risks of Testosterone Therapy
While Testosterone Replacement Therapy can significantly improve symptoms, it is associated with specific risks and requires diligent medical supervision. One of the most common adverse effects is polycythemia. This thickening of the blood can potentially increase the risk of blood clots, stroke, and heart attack. Studies suggest the risk of polycythemia may be higher with injectable forms of testosterone compared to transdermal methods.
TRT also necessitates caution regarding the prostate gland, and patients must be screened before treatment begins. Testosterone therapy has not been shown to cause prostate cancer, but it can potentially accelerate the growth of an already existing, undiagnosed cancer. For this reason, men on TRT require regular monitoring of their Prostate-Specific Antigen (PSA) levels, especially if they are over the age of 40.
Regular monitoring is a mandated component of TRT to manage these potential issues effectively. Physicians will regularly order blood tests to check the hematocrit level every three to six months to screen for polycythemia. If hematocrit levels become too high, the testosterone dose may be adjusted or temporarily halted.