You must be a 4th year? I wouldn't sweat it too much unless you have testing requirements at the end of this. But if you are looking for decent clinical performance, here's a brief list of things you should know pretty well to really shine right from the start:
1. Know diabetes pathophys and treatment pretty well. Know how to dose insulin inpatient and outpatient and what diabetic screening needs to be done (eye and foot exams, interval a1c), etc.
2. Know the adrenal gland and its various nuances (addison's, cushing, etc) and pathophys (cortex and medullary levels and what they make)
3. Know the pituitary and all of its woes (adenomas, hypopituitarism, etc)
4. Brush up on the thyroid pathophys and common disorders (hypothyroidism and its causes, hyperthyroidism and its causes)
If you know those, you will go a long way in dealing with common problems. Then you can learn more about the specifics on rotation, such as MEN syndromes, reproductive hormone related disorders, etc.