Testosterone

In men, testosterone plays an important role in the development of male reproductive tissues including the testis and prostate, as well as promoting secondary sexual characteristics such as increased muscle, bone mass, and hair growth. (7,8)  Additionally, testosterone is essential for health and well-being, stamina, sexual function, cardiovascular health, and immune protection. (9,10,11,12)  Testosterone measurements are typically used for clinical evaluation of hypogonadism in males and hyperandrogenic states in females. (13,14,15)

In blood, only 1 to 15% of testosterone is in its unbound or biologically active form.  The remaining testosterone is bound to serum proteins. Unbound testosterone enters the saliva via intracellular mechanisms, and in saliva the majority of testosterone is not protein-bound. (16)  The serum-saliva correlation for testosterone is very high for males, but only modest for females, possibly because women’s values often fall near the bottom of the measurable range for both serum and saliva immunoassay kits. (17,18)

References

1. Labrie, F., Luu-The, V., Bélanger, A., et al. (2005).  Is dehydroepiandrosterone a hormone? J Endocrinol, 187(2), 169-96.
2. Nakamura, Y., Hornsby, P.J., Casson, P., et al. (2008).  Type 5 17β-hydroxysteroid dehydrogenase (AKR1C3) contributes to testosterone production in the adrenal reticularis. J Clin Endocrinol Metab, 94(6), 2192-98.
3. Burger, H.G. (2002). Androgen production in women. Fertil Steril, 77(Suppl 4), S3-5.
4. Labrie, F., Bélanger, A., Cusan, L., Candas, B. (1997).  Physiological changes in dehydroepiandrosterone are not reflected by serum levels of active androgens and estrogens but of their metabolites: Intracrinology.  J Clin Endocrinol Metab, 82(8), 2403-9.
5. Ankarberg, C., Norjavaara, E. (1999).  Diurnal rhythm of testosterone secretion before and throughout puberty in healthy girls: Correlation with 17β-estradiol and dehydroepiandrosterone sulfate.  J Clin Endocrinol Metab, 84(3), 975-84.
6. Diver, M.J., Imtiaz, K.E., Ahmad, A.M., et al. (2003).  Diurnal rhythms of serum total, free and bioavailable testosterone and of SHBG in middle-aged men compared with those in young men. Clin Endocrinol (Oxf), 58(6), 710-17.
7. Rogol, A.D., Clark, P.A., Roemmich, J.N. (2000).  Growth and pubertal development in children and adolescents: Effects of diet and physical activity.  Am J Clin Nutr, 72(2 Suppl.), 521S-28.
8. Snyder, P.J., Peachey, H., Berlin, J.A., et al. (2000). Effects of testosterone replacement in hypogonadal men.  J Clin Endocinol Metab, 85(8), 2670-77.
9. Tibblin, G., Adlerberth, A., Lindstedt, G., Björntorp, P. (1996).  The pituitary-gonadal axis and health in elderly men: A study of men born in 1913.  Diabetes, 45(11), 1605-9.
10. Davis, S.R., Tran, J. (2001). Testosterone influences libido and well being in women. Trends Endocrinol Metab, 12(1), 33-7.
11. Wang, C., Alexander, G., Berman, N., et al. (1996). Testosterone replacement therapy improves mood in hypogonadal men: A clinical research center study. J Clin Endocrinol Metab, 81(10), 3578-83.
12. Malkin, C.J., Pugh, P.J., West, J.N., et al. (2006). Testosterone therapy in men with moderate severity heart failure: A double-blind randomized placebo controlled trial.  Eur Heart J, 27(1), 57-64.
13. Bhasin, S., Bremner, W.J. (1997). Clinical review 85: Emerging issues in androgen replacement therapy.  J Clin Endocrinol Metab, 82(1), 3-8.
14. Gibson, M., Lackritz, R., Schiff, I., Tulchinsky, D. (1980). Abnormal adrenal responses to adrenocorticotropic hormone in hyperandrogenic women.  Fertil Steril, 33(1), 43-8.
15. Rodin, A., Thakkar, H., Taylor, N., Clayton, R. (1994). Hyperandrogenism in polycystic ovary syndrome: Evidence of dysregulation of 11β-hydroxysteroid dehydrogenase.  N Eng J Med, 330(7), 460-65. 
16. Vining, R.F., MicGinley, R.A. (1987). The measurement of hormones in saliva: Possibilities and pitfalls.  J Steroid Biochem, 27(1-3), 81-94.
17. Wang, C., Plymate, S., Nieschlag, E., Paulsen, C.A. (1981). Salivary testosterone in men: Further evidence of a direct correlation with free serum testosterone.  J Clin Endocrinol Metab, 53(5), 1021-24.
18. Rollin, G. (2010). The trials of testosterone testing.  Clin Lab News, 36(8), 1-5.