Menopause is defined as having occurred 12 months after the woman’s last menses and is the result of depletion of viable ova and the cessation of ovulation. The average age is about 51 for women of European descent and somewhat younger for African Americans and Hispanic women of Mexican descent. The process usually begins about 5 years prior to the final menses with inconsistent and decreasing ovarian estradiol syn thesis. This leads to increasingly irregular menstrual periods. In addition many women experience one or more of a range of symptoms including hot flashes, vaginal irritation, sleep disruption, fatigue, mood lability, changes in hair texture and distribution, and weight gain. The exact symptoms and the severity of them vary greatly from one individual to another.

Changes in hormone levels in the years just before and after the menopause are shown in Figure 1. As the store of viable follicles is depleted, ovarian estradiol synthesis decreases and eventually ceases, and estrone from the peripheral aromatization of androstenedione becomes the main circulating estrogen. Some of this estrone can be converted to estradiol by 17β-HSD  so that low levels of estradiol remain after menopause. Peripheral aromatization takes place largely in adipose tissue, so that levels of circulating estrone and estradiol in obese women are substantially higher than in women of normal weight. The steep decline of inhibins A and B takes place 2–4 years prior to the last menses. The rise in FSH, due to declining E2 and inhibin levels, is steeper than that of LH, which is primarily reflective of E2 levels. Both FSH and LH remain elevated for the remainder of the individual’s lifetime, about 9-fold and 4-fold greater than premenopausal levels, respectively.

Fig1. Perimenopausal hormonal changes. The graph depicts changes in estradiol (red), the inhibins (green), and the gonadotrophins (blue) for the 4 years prior to and the 3 years following the last menstrual period (indicated by 0 on the x-axis). Inhibins A and B levels fall to or below the limit of detectability by two years prior to the last menstrual period and gonadotrophins remain elevated during the remainder of life.

As discussed in section V following, estrogens have effects on many tissues and physiological processes outside of the reproductive system, such as bone. The idea of replacing the estrogen lost at menopause to alleviate the perimenopausal symptomology as well as to offset the declines in these extrareproductive systems has been around since the 1950s. Recent assessments of this type of hormone replacement therapy approach will be discussed in section VI, Clinical Aspects.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم شؤون المعارف يباشر أعماله الدورية لجرد إصداراته

العتبة العباسية المقدسة تواصل استلام التبرعات لدعم الشعبين الإيراني واللبناني

قسم الشؤون الفكرية يقدم محاضرة ثقافية لوفد شبابي من بغداد

جمعية العميد تصدر الكتاب الثامن من سلسلة كنوز الآل

المزيد

الآخبار الصحية

عادة نهارية شائعة قد تخفي مشكلات صحية كامنة

الخوف من العيادات الطبية.. أسباب نفسية خفية لدى البالغين

"علكة مبتكرة" تستهدف ميكروبات الفم المسببة للسرطان

دخان حرائق الغابات قد يرفع خطر الإصابة بأنواع من السرطان

المزيد

الآخبار التكنلوجية

منهج جديد باستخدام الساعات الذرية يعيد طرح سؤال: ما طبيعة الزمن؟

اكتشاف آلية خلوية تمنع تكوّن الألياف المرتبطة بألزهايمر

دراسة تكشف أدلة على احتمال وجود محيط قديم بالمريخ

تيم كوك ينهي 15 عاما في قيادة "أبل"

المزيد

مواضيع ذات صلة

Uterine Effects of Estrogen and Progesterone

Chemistry and Metabolism of Female Steroid Hormones: Feedback Effects on the Hypothalamus and Pituitary

Control of the Ovary by the Hypothalamus and Pituitary

Synthesis of Progesterone and Estrogens

Female Steroid Hormones

The Androgen Receptor

Hypothalamic-Pituitary-Testis Axis: Feedback Control

Causes of Destructive (Low RAIU) Thyrotoxicosis

Causes of Hyperthyroidism

Hypothalamic-Pituitary-Testes Axis: Hormonal Control of the Testis

Sex Hormone-binding Globulin

Modification of Testosterone in Target Tissues