Effects of alcohol on female endocrine function

Alcohol Health & Research World, Spring, 1991 by Judith S. Gavaler

The female endocrine system--the system of glands and the hormones they produce--is responsible for, among other things, maintaining reproductive capacity in premenopausal women. Alcohol has been shown to affect the endocrine systems of premenopausal and postmenopausal women in different ways.

Sexually mature women can be categorized in two groups based on the functioning of their ovaries.

The first group comprises women in whom the cyclic fluctuations in levels of reproductive hormones produced by the ovaries reflect the process of development of an egg. The occurrence of these cycles defines reproductive capacity. The second group comprises women in whom cyclic ovarian function has ceased (in other words, they have attained menopause), and who are classified as being postmenopausal. Women today can expect to live one-third of their lives in the postmenopausal state.

There are two ways for a woman's body to reach the postmenopausal state. The first is via a natural internal process in which the cycles of development and maturation of eggs contained in follicles(1) become less and less regular, eventually ceasing to occur. The second route is by the surgical removal of the ovaries. It should be pointed out that hysterectomy, or the surgical removal of the uterus, does not produce the menopause. Although hysterectomy eliminates the site for menstrual bleeding, which is a convenient marker of cyclic ovarian function, the ovaries can continue to function until the menopause occurs.

It is important to draw a clear distinction between women with cyclic ovarian functioning and women in the postmenopausal state, because disruptions of the endocrine system by alcohol would be expected to differ in the two cases.

ALCOHOL AND FEMALE ENDOCRINE STATUS

No definitive data on endocrine function in women who drink alcohol moderately during the reproductive years are available. And although information about the effects of alcohol abuse on the menstrual cycle and hormone levels in women is available, no studies have documented the point at which consumption of alcohol begins to cause deleterious effects. The situation with postmenopausal women is different: in addition to studies evaluating postmenopausal women who are alcoholics, there are studies evaluating the effects of moderate alcohol consumption on the hormonal status of healthy postmenopausal women.

A variety of clinical settings have been used to evaluate the effects of alcohol consumption on hormone levels and on reproductive function in women. Yet, although the effects themselves are generally known, the specific mechanisms have not all been elucidated. A likely explanation for our relative lack of knowledge about effects of alcohol on female hormones and reproductive function is that it is difficult to study women during their reproductive years because of the continual changes in hormone levels as part of the menstrual cycle itself. The fact that women have been studied less well than men has led some to suggest that bias on the part of investigators is responsible (Vannicelli and Nash 1984). Few studies have evaluated effects of alcohol consumption on the hormonal status of postmenopausal women, even though, in their case, complex hormonal variation is no longer a complicating factor. Sustained interest in alcohol effects in general among the elderly is of rather recent vintage.

In biomedical research, the ultimate goal is to elucidate the mechanisms of clinical findings. For ethical reasons, a great deal of biomedical alcohol research has made use of animal models. Indeed, studies using animals have produced considerable amounts of data about the effects of alcohol on reproductive function and levels of hormones in the blood. There are limitations, of course; for example, female rodents do not go through a menopausal process and cannot serve as models for natural menopause in humans (Gavaler and Rosenblum 1987). Female animals that have had their ovaries surgically removed, however, have been used as models for postmenopausal women who have had their ovaries removed (as many as 22.5 percent of postmenopausal women have undergone ovariectomies; Howe 1984). Studies using such animals have confirmed clinical findings about alcohol's effects on hormones in humans. More importantly, animal studies have extended the information obtained from studies involving humans. Research using animals will continue to be a powerful tool for elucidating the effects of alcohol on hormonal functioning in women.

EFFECTS OF ALCOHOL DURING THE REPRODUCTIVE YEARS

Based on our knowledge of basic reproductive physiology, alcohol might be expected to cause irregularities in the menstrual cycle and the development and maturation of the follicle that contains the egg cell. Alcohol might affect the endocrine cells, which produce hormones such as progesterone and estrogens, thereby altering the amounts of hormones produced during the phases of the menstrual cycle. To review the introductory material in the article by Doria (pp. 101-103): The granulosa cells of the follicle nurture the growing egg by producing estrogens (estrone and estradiol). The corpus luteum, which is formed from the ruptured follicle following ovulation, produces progesterone, the hormone that prepares and maintains the lining of the uterus for a fertilized egg. Low progesterone levels would therefore reflect the absence of ovaluation and the corpus luteum.