What are the typical hormonal lab findings in a patient with primary hypogonadism?

From the Guidelines

Primary hypogonadism is characterized by low serum testosterone levels, typically <300 ng/dL, accompanied by elevated gonadotropins, including luteinizing hormone (LH) and follicle-stimulating hormone (FSH) 1.

Key Hormonal Findings

• Low total testosterone levels, usually below 300 ng/dL
• Elevated LH and FSH levels, indicating testicular failure to produce testosterone despite increased pituitary stimulation
• Decreased free testosterone, representing the biologically active fraction of testosterone
• Potential decrease in inhibin B levels, which normally provides negative feedback to the pituitary

Importance of Additional Tests

• Measurement of sex hormone-binding globulin (SHBG) in males to accurately calculate free testosterone, especially in conditions like obesity, diabetes, and liver disease that can affect SHBG concentrations
• Assessment of morning serum free testosterone by equilibrium dialysis and SHBG level in patients with obesity to evaluate hypogonadism accurately

Distinguishing Primary from Secondary Hypogonadism

• Primary hypogonadism: low sex hormones (testosterone) with high gonadotropins (LH and FSH)
• Secondary hypogonadism: both low sex hormones and low gonadotropins due to pituitary or hypothalamic dysfunction, as indicated by low LH and FSH levels 1

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Hormonal Lab Findings in Primary Hypogonadism

The typical hormonal lab findings in a patient with primary hypogonadism include:

• Low total testosterone levels
• Elevated luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels, which distinguish primary hypogonadism from secondary hypogonadism 2
• The combination of low testosterone and high LH and FSH levels is characteristic of primary hypogonadism, as the pituitary gland produces more gonadotropins in an attempt to stimulate the testes to produce testosterone 3

Comparison to Secondary Hypogonadism

In contrast to primary hypogonadism, secondary hypogonadism is characterized by:

• Low or inappropriately normal gonadotropin levels along with low total testosterone levels 4
• This is because the hypothalamus and/or pituitary gland is not functioning properly, leading to decreased production of gonadotropin-releasing hormone (GnRH) and subsequently LH and FSH

Clinical Implications

The hormonal lab findings in primary hypogonadism have important clinical implications, including:

• The need for testosterone replacement therapy to induce and maintain secondary sexual characteristics and sexual function 2, 5
• The potential for fertility treatment, such as gonadotropin therapy or GnRH supplementary/replacement therapy, in patients with primary hypogonadism who desire to father children 4
• The importance of monitoring gonadotropin levels, in addition to testosterone levels, to assess the adequacy of androgen replacement therapy 3