Module 3

1. Module 3

1.27. Page 4

Lesson 1

Module 3—The Male and Female Reproductive Systems

Lesson Summary

In this lesson you considered the following focusing questions:

What are the male reproductive hormones?
How do hormones maintain homeostasis in the male reproductive system?
What role do the male hormones play in regulating the primary and secondary sex characteristics?

Although gender is first controlled by the chromosome arrangement received from our parents, it is hormones that lead to sexual development, gamete production, and the eventual continuation of the species.

Male hormone production begins in an embryo in the uterus. The process of sexual maturation happens during puberty, with the increase in production of GnRH from the hypothalamus. GnRH then causes the anterior pituitary to produce both FSH and LH. The production of FSH causes the testes to start producing sperm and the hormone inhibin, which feeds back negatively to the pituitary to control further production of FSH. While LH causes the testes to produce testosterone, high levels of the hormone provide a negative feedback control of the hypothalamus and pituitary to regulate LH production, thus also regulating testosterone production. Testosterone is responsible for the proper development and maturation of the primary and secondary sex characteristics.

Chemical hormone control of the mature male reproductive system causes a peak in testosterone levels during three major times in a male’s life: in utero, at birth, and during puberty. After puberty, testosterone levels stay at a steady rate for most of the remainder of a man’s life. Levels of testosterone can begin to drop at about age 40, a condition sometimes referred to as andropause. Although a male continues to produce testosterone throughout his life, sperm count is reduced as he ages.

Understanding the scientific effect of testosterone on the body has led to the technological production of synthetic anabolic steroids. Although steroids can sometimes be used to treat disorders, like naturally low testosterone levels (called hypogonadism), anabolic steroids affect society in a much greater way through their misuse. The desire to look or perform better may lead some individuals to misuse anabolic steroids, even when they are informed of the risk factors involved.

Lesson Glossary

Consult the glossary in the textbook for other definitions that you may need to complete your work.

anabolic steroids: male steroid hormones (including testosterone) that enhance muscle development

follicle-stimulating hormone (FSH): a hormone produced by the anterior pituitary; causes spermatogenesis in males

gonadotropin releasing hormone (GnRH): a hormone produced by the hypothalamus; stimulates the anterior pituitary to produce FSH and LH

interstitial cell stimulating hormone (ICSH): also known, in the male, as the luteinizing hormone

luteinizing hormone (LH): a reproductive hormone produced by the anterior pituitary; causes the release of testosterone in males, where it is also known as the interstitial cell stimulating hormone (ICSH)

In females, LH triggers ovulation, stimulates the formation of the corpus luteum, and acts with FSH to stimulate estrogen production.

steroids: a group of lipids derived from cholesterol

All male and female sex hormones are steroids.