The endometrium

Abstract

Light microscopy has been supplemented by descriptions of electron microscopy both transmission and scanning in the proliferative and secretory phases. Emphasis is placed on the subcellular organelles that play a role in carbohydrate and protein synthesis so important for the appropriate functioning of the endometrium. Some of the enzymes involved in the various carbohydrate metabolic pathways are described and their role as histochemical indicators delineated. Protein metabolism and the role of the nucleolus in RNA synthesis is considered together with the lysosomal theory of menstruation. As endometrium is a hormonal end organ current views are given on the action of the steroid estrogens and progesterone together with the importance of the cytoplasmic receptors. These indicate that the receptors may play a modulating role in steroid hormone action as the tissue concentration of steroid may be controlled not only by the plasma hormone concentration but by changes in the cytoplasmic receptor activity. Of the proteins synthesized by the uterus blastokinin may have a particularly important role in implantation. With this background of endocrinology and molecular biology, the endometrium should be regarded as a true indicator of the hormonal events that surround ovulation. This is clearly not an all or none phenomenon indicated by a simple diagnosis of 'secretory phase', but should be regarded as a changing process that may be dated accurately. It then becomes rational to obtain serial outpatient aspiration biopsies to help elucidate the particular endocrine problems of 'defective ovulation'. No attempt is made to provide a description of the conventional pathology of the endometrium, but the judicious use of biopsies has been shown to illuminate one's understanding of abnormal endocrine events.