I have a patch of hair missing on right calf, 9" in length and 4" in width. (photo)

I am a 30 yr old Male, the patch of hair missing has steadily grown. About 6 months ago, it was about 2" by 2" in size missing and is now 9" by 4". I also have been experiencing depression, weight gain, and muscle weakness. I was on Accutane from Feb to April of this year for acne. This is the only medication I was taking. I run regularly and diet to keep fitness up for Navy standards. I have been in the Navy for 5 years, I have never experienced problems with weight. I enjoy a healthy life style.