Is it possible to have undetectable cortisol levels in secondary adrenal insufficiency?

Yes, you can certainly have undetectable cortisol in central AI. Low IGF-1 and low-normal FT4 would suggest hypopituitarism. Do you have a testosterone level? I would perform a GH stimulation test. An abnormal test would confirm pituitary pathology. Before this, however, I would carefully investigat...

I agree with Dr. @Dr. First Last, it is very strange to see these elevated testosterone levels. And also to start thyroid replacement while trying to work through this.

I have a few clarifying questions. What work does he do? What are his hobbies/athletic interests? Do you have a testicular exam on...