Hydroxysteroid (17β)-dehydrogenase 1–deficient female mice present with normal puberty onset but are severely subfertile due to a defect in luteinization and progesterone production

Hydroxysteroid (17β)-dehydrogenase type 1 (HSD17B1) catalyzes the conversion of low active 17-ketosteroids, androstenedione (A-dione) and estrone (E1) to highly active 17-hydroxysteroids, testosterone (T) and E2, respectively. In this study, the importance of HSD17B1 in ovarian estrogen production was determined using Hsd17b1 knockout (HSD17B1KO) mice. In these mice, the ovarian HSD17B enzyme activity was markedly reduced, indicating a central role of HSD17B1 in ovarian physiology. The lack of Hsd17b activity resulted in increased ovarian E1:E2 and A-dione:T ratios, but we also observed reduced progesterone concentration in HSD17B1KO ovaries. Accordingly with the altered steroid production, altered expression of Star, Cyp11a1, Lhcgr, Hsd17b7, and especially Cyp17a1 was observed. The ovaries of HSD17B1KO mice presented with all stages of folliculogenesis, while the corpus luteum structure was less defined and number reduced. Surprisingly, bundles of large granular cells of unknown origin appeared in the st...