Hormone Evaluation for Men with Low Libido
In men with symptoms of low libido, a morning total testosterone level should be measured as the primary hormonal assessment, along with luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to distinguish between primary and secondary hypogonadism. 1, 2
Primary Hormonal Assessment
Total testosterone: Should be measured in the morning when levels are highest
- Use an accurate and reliable assay
- Normal range: 450-600 ng/dL 2
Sex hormone-binding globulin (SHBG):
- Should be checked in men with total testosterone levels close to the lower limit
- Often low in diabetes and associated with lower testosterone levels 1
Free testosterone calculation:
- Important to assess bioavailable testosterone
- May reveal hypogonadism in 50% of cases where total testosterone appears normal 3
LH and FSH levels:
- Essential to determine the cause of hypogonadism (primary vs. secondary)
- Primary hypogonadism: Low testosterone with elevated LH/FSH
- Secondary hypogonadism: Low testosterone with low or normal LH/FSH 2
Clinical Interpretation
Primary Hypogonadism Pattern
- Low testosterone + elevated LH/FSH
- Indicates testicular failure (congenital or acquired)
- Causes include cryptorchidism, orchitis, or orchidectomy 4
Secondary Hypogonadism Pattern
- Low testosterone + low/normal LH/FSH
- Indicates hypothalamic-pituitary dysfunction
- Causes include pituitary tumors, trauma, radiation, or idiopathic gonadotropin deficiency 4
Additional Considerations
Prolactin: Consider checking if secondary hypogonadism is suspected
- Hyperprolactinemia occurs in approximately 1.8% of men with sexual dysfunction 3
- Important to rule out pituitary adenomas
Estradiol: May be relevant in some cases
- Elevated levels can affect testosterone/estrogen ratio
- Can contribute to sexual dysfunction 2
Clinical Pearls and Pitfalls
- A single testosterone measurement is insufficient; confirm low values with a second morning measurement
- Physical signs of hypogonadism (testicular atrophy) cannot reliably predict biochemical hypogonadism 3
- Obesity is a major confounder in testosterone assessment 1
- Diabetes is associated with lower testosterone levels compared to age-matched men without diabetes 1
- Free testosterone measurement is crucial as it can identify hypogonadism in men with borderline total testosterone levels 3
- Testosterone therapy in symptomatic hypogonadal men improves sexual function, well-being, muscle mass, strength, and bone density 1
By following this systematic approach to hormonal evaluation in men with low libido, you can accurately identify the underlying hormonal imbalances and determine the appropriate treatment strategy to address the patient's symptoms.