Hormones in the Male Reproductive System – Testosterone


Hormones in the Male Reproductive System – Testosterone

Hormones play an important role in the male reproductive system. They are responsible for the sex drives of men and affect their reproductive abilities as well. Unlike women, who have cyclical hormonal secretion and fluctuations according to their menstrual cycle, hormone in men tend to stay relatively constant from the onset of puberty and well into their reproductive years.

Important Hormones in the Male Reproductive System

The most important hormones involved in the male reproductive system are listed below and also from where it is been secreted and produced.

  • Gonadotropin-Releasing Hormone (GnRH) is secreted from the hypothalamus,
  • Follicle-Stimulating Hormone (FSH), and Luteinizing Hormone (LH) is produced by the anterior portion of the pituitary gland,
  • The gonads produces Estrogen (Estradiol) and Testosterone.

The Hypothalamic-pituitary Gonadal Axis (HPG) refers to the hypothalamus, pituitary and gonadal glands and it plays a critical role in the development and regulation for the various body systems, such as reproductive and immune systems. Any fluctuation in this axis causes changes in the hormones which is produced by each gland and in turn it causes various local and systemic effects on the body.

Testosterone and its function in men

Perhaps the most popular of the hormones in the male reproductive system is the Testosterone. About 95% of the testosterone is produced by the Leydig (interstitial) cells of the testes and the rest is produced by adrenal glands.  Among FSH, LH and Testosterone, testosterone is the most important hormone which plays a major role in the normal growth and development which includes the development of the body, facial hair, the functions of the larynx which in turn leads to the change in the voice after puberty, the enlargement of the genitals and the secondary sex characteristics in men. Testosterone combines together with FSH to stimulate the production of sperm in men and regulates the flow of the same during sexual intercourse. On an average, it is present in relatively constant concentrations in men who are of reproductive age and are healthy and sexually active. The average range of Testosterone concentrations in adult men is between 270 to 1070 ng/dL with an average of 670 ng/dL. In addition, the levels peak during early adulthood in the 20s and stay constant throughout the reproductive years. Testosterone decreases 1% to 2% per year after 40 years of age.
When the level of testosterone is low, the symptoms in men includes decreased muscle and bone strength, loss of energy, low fertility, decrease in sex drive, poor erections, low sperm count and lower fertility.
Another key point to note here is that Testosterone is both free and total wherein the former is not bound to the proteins such as Albumin and the Sex Hormone Binding Globulin (SHBG) whereas the latter is bound to them.

Testosterone is also known for the hormone replacement treatments that fertility specialists recommend to aging men keen to restore their virility and enliven their sex lives due to sagging loss of the latter. However, experts sometimes caution about the side effects of hormone replacement in terms of risks of prostate cancer and other ailments.
Testosterone regulates the numerous functions along with the sperm production in men such as sex drive, bone mass, fat distribution, muscle size and strength, red blood cell production.
In this article, we have introduced the various hormones in the male reproductive system and explored the role of testosterone. We will be discussing the role of the other hormones in the upcoming blogs.

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