REPRODUCTIVE HORMONES AND ORAL CONTRACEPTIVES
Section I. INTRODUCTION
For many years people have attempted to better understand the reproductive
process. The reasons why people have desired to learn more about reproduction are
many. Some wish to identify and alleviate problems that prevent them from having
children. Others want to identify and use ways to prevent pregnancy. You will dispense
drugs that affect the reproductive process. Hence, you should be familiar with these
agents and how they affect the reproductive system as well as the entire body.
There are three main categories of reproductive hormones, estrogens,
progestins, and androgens.
a. Estrogens. In females, estrogens are secreted by the developing ovarian
follicle and by the corpus luteum (see Lesson 6, para 6-11b). During pregnancy, the
placenta secretes estrogens. Estrogens are responsible for the development of the
uterus, vagina, fallopian tubes, and breasts. Estrogen also produces such physiological
effects as accelerating growth at puberty (causes epiphyses of long bones to close),
increasing clotting factors in circulation, and decreasing bone reabsorption. Estrogen
produces female secondary sex characteristics (like distribution of fat, development of
pubic hair, high-pitch voice, and increased skin pigmentation). In males, there is limited
estrogen secretion by the adrenal glands.
b. Progesterone. Progesterone is the hormone that prepares the female's body
for pregnancy and helps maintain pregnancy. That is, this hormone decreases the
motility of the uterus, allowing the fertilized egg to implant and remain implanted in the
uterus. Progesterone also develops the milk-secreting cells of the breasts. Decreased
levels of progesterone cause irregularity of the menstrual cycle.
c. Androgens. In males, the androgens are produced in the testes.
Testosterone is the principal and most powerful androgen. Physiologically, the
androgens affect the following:
(1) Development of the testes, vas deferens, the prostate, seminal
vessicles, penis, and scrotum.
Growth at puberty and the length of long bones (closes epiphyses of