Measurement of testosterone in the saliva is used in the diagnosis and monitoring of primary and secondary hypogonadism, in disorders arising from pathological conditions in the testes, or in disorders of the hypothalamus and pituitary gland. In addition, it is used to investigate impotence in men and to monitor excessive hair growth (hirsutism) and masculinization due to tumors, polycystic ovaries, and adrenogenital syndromes in women.
The measurement of testosterone, along with cortisol in saliva, is a useful laboratory tool in research regarding stress and sports medicine.
Testosterone is an anabolic steroid hormone synthesized by androstenedione in Leydig cells in the testes and in smaller amounts in the ovaries. Small amounts of testosterone are also produced by the adrenal glands in both sexes. In both men and women, part of the total testosterone production takes place 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 continue to produce testosterone and other androgens, which then serve as precursor molecules for the synthesis of estradiol. Testosterone secretion shows a daily (circadian) rhythm, with the highest levels being observed early in the morning and the lowest around midnight.
In men, testosterone plays an important 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 and are related to the picture of aging, such as loss of muscle mass and bone density, decreased physical endurance, decreased memory, and decreased libido.
In the blood, only a small percentage ranging from 1 to 15% (usually 2 - 3%) of testosterone 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 (small amount). Only unbound (free) testosterone has a biological effect.
Unbound testosterone enters saliva through certain intracellular mechanisms. In saliva, most testosterone is not bound to proteins. Measurement of salivary testosterone has great clinical value because it represents the filtered and biologically active fraction of plasma testosterone and in addition, the concentration of testosterone in the 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, probably because testosterone levels in women 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 collection of the sample is non-invasive and easy, without the possible complications and inconvenience of blood sampling, while ensuring the sensitivity and accuracy of the measurements