Module 3 Lesson 4 - 3
Lesson 4 — Sex Development and Male Hormones
Hormonal Regulation of the Male Reproductive System
Read pages 493 - 495
Testosterone is produced by the interstitial cells (also called Leidig cells) located between the seminiferous tubules in the testes. Prior to birth during the embryonic stage, testosterone begins to be produced in the male reproductive system, and it is responsible for the development of the male sexual organs.
During childhood, the testosterone levels are low, but they increase during puberty. The increased levels of testosterone result in the development of primary and secondary sex characteristics (deepening of voice, increased muscle mass and muscle tone, facial hair, body hair, etc.) and the initiation of spermatogenesis.
For boys, the age that puberty starts varies greatly, but it is said to begin when gonadotropin releasing hormone (GnRH) production is increased by the hypothalamus. This hormone activates the anterior pituitary to release follicle stimulating hormone
(FSH) and luteinizing hormone (LH).
Negative Feedback Loop of Testosterone
The hormonal regulation of the male reproductive system is a negative feedback loop because inhibin and testosterone levels inhibit the production of gonadotropin releasing hormone (GnRH), leading to suppression of their own production.
The hypothalamus releases the gonadotropin releasing hormone (GnRH) and stimulates the anterior pituitary to release follicle stimulating hormone (FSH) and luteinizing hormone (LH). These two hormones have critical roles in both male and female reproductive systems.
In males, the follicle stimulating hormone (FSH) performs two major functions:
- FSH binds to Sertoli cells located in the seminiferous tubules and stimulates spermatogenesis.
- FSH stimulates Sertoli cells to produce inhibin.
Increased levels of inhibin result in suppression of follicle stimulating hormone (FSH) levels in the anterior pituitary.
The luteinizing hormone (LH) binds to interstitial cells and stimulates them to produce testosterone. When the concentrations of testosterone reach acceptable levels, testosterone triggers both the hypothalamus and the anterior pituitary to stop releasing
GnRH, FSH, and LH. When the levels testosterone drop, the hypothalamus begins to release gonadotropin releasing hormone (GnRH), which stimulates the anterior pituitary to start releasing follicle stimulating hormone (FSH) and luteinizing hormone
(LH) again.
Male Hormone Feedback System Summary
Testosterone and Aging
Beginning about age 40, the interstitial cell activities begin to decline, marking the start of andropause, otherwise known as male menopause. The gradual decline in the testosterone levels results in fatigue, depression, loss of muscle and bone mass, and reduction in spermatogenesis.
Did You Know?
Although testosterone often is associated with the male reproductive system, it is produced in females, too. Testosterone has an important role in maintaining bone strength, lean muscle mass, and libido.
The ovaries produce low levels of testosterone. The adrenal glands in both males and females produce low levels of testosterone, also.
Watch and Listen
To understand when the main periods of hormone production occur, what the hormones produced are, what the function of each hormone is, and how the hormones are regulated in the male body is very important. To help you develop a clear understanding of
the hormone control of the male reproductive system from utero, through puberty, and into aging, watch the following Biologix-14 video clip.
Going Beyond
Testosterone levels should be within normal ranges in both men and women. However, disorders of the body may need to be treated with various types of steroids. The use of anabolic steroids can have harmful effects, yet some body disorders require treatment through steroid use. Try to find why steroids may be used to help treat individuals with HIV infection, Addison's disease, arthritis, or any other disorder you may identify.