Salivary testosterone measurement is used to diagnose and monitor primary and secondary hypogonadism, disorders resulting from testicular pathology, or disorders of the hypothalamus and pituitary gland. It is also used to investigate impotence in men and hirsutism (excessive hair growth) and virilization due to tumors, polycystic ovaries, and adrenogenital syndromes in women.
Salivary testosterone measurement and cortisol are valuable laboratory tools in stress research and sports medicine.
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Testosterone is an anabolic steroid hormone synthesized by androstenedione in Leydig cells in the testes and in smaller amounts in the ovaries. The adrenal glands in both sexes also produce small amounts of testosterone. In men and women, part of the total testosterone production occurs in the peripheral tissues by converting the circulating molecules DHEA-S, DHEA, and androstenedione. In men, this peripheral conversion is not significant, but in women, it can account for up to 50% of testosterone production. In postmenopausal women, the ovaries and peripheral tissues produce testosterone and other androgens, which serve as precursor molecules for estradiol synthesis. Testosterone secretion shows a daily (circadian) rhythm, with the highest levels observed early in the morning and the lowest around midnight.
In men, testosterone plays a vital role in the development of reproductive tissues, including the testes and prostate, as well as in the development of secondary gender characteristics such as muscle growth, bone mass, and hair growth. In addition, testosterone is essential for health and wellness, endurance, sexual function, cardiovascular health, and the proper functioning of the immune system. Testosterone measurements are commonly used for the clinical evaluation of hypogonadism in men and testosterone overproduction conditions in women. Testosterone levels gradually decrease with age in men (andropause). The signs and symptoms of andropause are non-specific. They are related to the picture of aging, such as loss of muscle mass and bone density, decreased physical endurance, decreased memory, and decreased libido.
Only a tiny percentage, ranging from 1 to 15% (usually 2 - 3%), of testosterone in the blood is in unbound or biologically active form. The remaining testosterone binds to three serum proteins: sex hormone-binding globulin (SHBG) (44 - 78%), albumin (20 - 54%), and binding cortisol globulin (a small amount). Only unbound (free) testosterone has a biological effect.
Unbound testosterone enters saliva through specific intracellular mechanisms. Most testosterone in saliva is not bound to proteins. Measurement of salivary testosterone has excellent clinical value because it represents the filtered and biologically active fraction of plasma testosterone. In addition, the testosterone concentration in saliva is independent of the saliva flow rate.
The correlation between serum testosterone and saliva levels is very high for men and moderate for women. This is probably because women's testosterone levels are very low and often close to the lowest measurable point for both serum blood and saliva testing.
Measurements of hormones in saliva are an excellent choice because the sample collection is non-invasive and easy, without the possible complications and inconvenience of blood sampling, while ensuring the sensitivity and accuracy of the measurements.
