I think that a good understanding of endocrine physiology (including reproductive, for both male and female) is relatively high yield on Step 1. The best way I can suggest to study it is to read the Endocrine chapter in BRS Physiology both during your first and second year. Definitely read it and become as familiar with that chapter as you can when going through this material during your second year endocrine pathophysiology, pathology and pharmacology. For endocrine more than any other system, once you understand the physiology of it the pathology and pharmacology become pretty simple with less memorization required.