Endometrial dating correlated with progesterone levels

The aim of this work was to document the validity and usefulness of progesterone determination instead of endometrial biopsies as evidence for ovulation within a menstrual cycle. The presence of progesterone in amounts greater than 2 ng/ml of plasma was always associated with a secretory endometrium, ie, the endometrium was matured beyond cycle day 14 as diagnosed by classical histologic dating. The remarkable simplicity of quantitating luteal phase progesterone levels by this radioimmunoassay warrants their extended use for evaluating the physiology and the pathology of the corpus luteum.