Interpretation

In male patients:

Decreased testosterone levels indicate partial or complete hypogonadism. In hypogonadism, serum testosterone levels are usually below the reference range. The cause is either primary or secondary/tertiary (pituitary/hypothalamic) testicular failure.

Primary testicular failure is associated with increased luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels, and decreased total, bioavailable, and free testosterone levels. Causes include:

-Genetic causes (eg, Klinefelter syndrome, XXY males)

-Developmental causes (eg, testicular maldescent)

-Testicular trauma or ischemia (eg, testicular torsion, surgical mishap during hernia operations)

-Infections (eg, mumps)

-Autoimmune diseases (eg, autoimmune polyglandular endocrine failure)

-Metabolic disorders (eg, hemochromatosis, liver failure)

-Orchidectomy

Secondary/tertiary hypogonadism, also known as hypogonadotrophic hypogonadism, shows low testosterone and low, or inappropriately "normal" LH/FSH levels. Causes include:

-Inherited or developmental disorders of hypothalamus and pituitary (eg, Kallmann syndrome, congenital hypopituitarism)

-Pituitary or hypothalamic tumors

-Hyperprolactinemia of any cause

-Malnutrition

-Excessive exercise

-Cranial irradiation

-Head trauma

-Medical or recreational drugs (eg, estrogens, gonadotropin releasing hormone [GnRH] analogs, cannabis)

Increased testosterone levels:

-In prepubertal boys, increased levels of testosterone are seen in precocious puberty. Further workup is necessary to determine the cause of precocious puberty.

-In men, testicular or adrenal tumors or androgen abuse might be suspected if testosterone levels exceed the upper limit of the normal range by more than 50%.

Monitoring of testosterone replacement therapy:

Aim of treatment is normalization of serum testosterone and LH. During treatment with depot-testosterone preparations, trough levels of serum testosterone should still be within the normal range, while peak levels should not be significantly above the normal young adult range.

Monitoring of antiandrogen therapy:

Aim is usually to suppress testosterone levels to castrate levels or below (no more than 25% of the lower reference range value, typically <50% ng/dL).

In female patients:

Decreased testosterone levels may be observed in primary or secondary ovarian failure, analogous to the situation in men, alongside the more prominent changes in female hormone levels. Most women with oophorectomy have a significant decrease in testosterone levels.

Increased testosterone levels may be seen in:

-Congenital adrenal hyperplasia: Non-classical (mild) variants may not present in childhood, but during or after puberty. In addition to testosterone, multiple other androgens or androgen precursors, such as 17-hydroxyprogesterone (OHPG / 17-Hydroxyprogesterone, Serum), are elevated, often to a greater degree than testosterone.

-Prepubertal girls: Analogous to boys, but at lower levels, increased levels of testosterone are seen in precocious puberty.

-Ovarian or adrenal neoplasms: High estrogen values also may be observed and LH and FSH are low or "normal." Testosterone-producing ovarian or adrenal neoplasms often produce total testosterone values above 200 ng/dL.

-Polycystic ovarian syndrome. Hirsutism, acne, menstrual disturbances, insulin resistance and, frequently, obesity form part of this syndrome: Total testosterone levels may be normal or mildly elevated and uncommonly above 200 ng/dL.

Monitoring of testosterone replacement therapy:

The efficacy of testosterone replacement in female patients is under study. If it is used, then levels should be kept within the normal range for females at all times. Bioavailable or free testosterone levels should also be monitored to avoid overtreatment; see TTFB / Testosterone, Total, Bioavailable, and Free, Serum .

Monitoring of antiandrogen therapy:

Antiandrogen therapy is most commonly employed in the management of mild-to-moderate idiopathic female hyperandrogenism, as seen in polycystic ovarian syndrome. Total testosterone levels are a relatively crude guideline for therapy and can be misleading. Therefore, bioavailable or free testosterone should also be monitored to ensure treatment adequacy; see TTFB / Testosterone, Total, Bioavailable, and Free, Serum. However, there are no universally agreed biochemical end points and the primary treatment end point is the clinical response.