How much do you know about menarche and female reproductive hormones?

Menarche and Effects of Oestrogen and Progesterone on Body Tissues

• Menarche is the onset of menstruation which is preceded by the release of hormones from the pituitary gland and ovaries.
• Human growth hormone (hGH) causes the growth spurt which begins 3 to 4 years before the menarche.
• Increasing quantities of oestrogen are secreted by the ovaries and reduce hGH secretion, slowing down physical growth as menarche approaches.
• GnRH induces the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland, which, in turn, induce the secretion and release of oestrogen and progesterone into the circulation.
• Hormonal changes persist until after the age of 40 when changes presaging the menopause begin.
• The rapid rise of LH, mediated by kisspeptin and GnRH, induces the onset of menarche, but other factors are also involved, including an increase in the fat-to-lean ratio of body composition.
• The average age at menarche fell from 15-17 years to 13-13.5 years between the early 1800s and the mid-1900s due to better childhood nutrition.
• The greater amount of body fat in girls today permits the greater aromatization of androgens to oestrogens, leading to the LH surge that precedes the menarche.
• The menarche may be delayed in women who are of low body weight, such as ballet dancers, women who have anorexia nervosa, or those who exercise excessively.
• Oestradiol is the most active and predominant oestrogen in the reproductive years, transported in the blood to tissues that have oestrogen-binding receptors.
• Oestradiol stimulates the growth of the vulva and the vagina, causing proliferation of both the epithelial and the muscular layers.
• Oestradiol causes endometrial proliferation, stimulating the growth of the glands and stroma, as well as the growth of the muscular layers of the uterus.