Physiology of the menstrual cycle

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Abstract
Modern techniques of bioassay have permitted correlation of hormonal secretion with genital tissue changes during the normal menstrual cycle. During the follicular phase, estrogen secretion rises while other hormone levels are low. At ovulation luteinizing hormone and follicle-stimulating hormone surges are associated with falling estrogen levels. Secretions of progesterone and estrogen again are characteristic of the luteal phase ending with menstruation. Gonadotrophin-releasing hormones are detectable just before the luteinizing hormone and follicle-stimulating hormone surges. Basal body temperature rises with ovulation and is still the most reliable clinical indicator, although ferning and spinnbarkeit (when present) are also quite helpful. Vaginal smears are probably less useful except in the hands of experienced observers. The correlation of hormonal secretion with genital tissue changes during the normal menstrual cycle has been made possible employing modern techniques of bioassay. Estrogen secretion rises and other hormone levels are low buring the follicular phase. Luteinizing hormone (LH) and follicle stimulating hormone (FSH) surges are associated with decreasing estrogen levels at ovulation. The luteal phase ending with menstruation is characterized by the secretion of progesterone and estrogen. Prior to LH and FSH surges gonadotrophin-releasing hormones are detectable. The rise of basal body temperature with ovulation is the most reliable indicator of ovulation although ferning and spinnbarkeit are also useful. Vaginal smears may be of use when handled by experienced people.