The endometrium in natural and artificial luteal phases

The normal human endometrium reacts precisely and sen–sitivelyto any hormonal stimulation with predictable changes. If thecorpus luteum develops normally after ovulation, the progesteronesecreted induces specific changes in endometrial glandular andstromal cells that can be dated by dally fine–structuralalterations. With corpus luteum deficiency the endometrial differentationis delayed and remains incomplete. The defect in the differentiationof glands and stroma varies in their distribution and intensityand may be dissociated or coordinated depending upon the causeof the corpus luteum deficiency. The administration of naturalprogesterone in the second half of the cycle prolongs the lutealphase and may result in hypersecretion of glands. In contrast,therapy with synthetic gestagens depresses glandular secretion,induces glandular atrophy and decidualization of the stroma.The various synthetic gestagens differ both quantitatively andqualitatively in their action; depending upon the dosage giventhe endometrium remains in abortive or arrested secretion, domlphenedepresses normal secretion by its antioestrogenk effect whichcauses deficient oestrogen priming. On the other hand, clomiphenecounteracts excessive oestrogen and will normalize the secretionin a deficient luteal phase that was preceded by follicularpersistency. In the artificial cycle, depending upon the stateof endogenous hormonal stimulation, the patients will benefiteither from clomiphene or gonadotrophin to maintain or normalizetheir secretory endometrium.