Could be a lot of things, but I doubt it's thyroid related. I've read that people with type II diabetes often get brown patches on their skin, especially knees, elbows, neck and arms. Have you ever had blood sugar problems or insulin resistance?
What do you mean you have a "thyroid level of zero"?
I hope you mean 8,000 IU vitamin D and not 80,000. You can take too much Vitamin D. Have it tested when you have your next blood test. Kidney stones could mean too much calcium, and the Vitamin D could make this condition worse. Too much Vitamin D can also cause other kidney problems. Consult with your doctor and have him/her do a full blood panel.
Some kidney diseases cause skin hyperpigmentation (dark patches) so I think you definitely need to see a specialist about this. I reckon that is the most likely explanation.
Another possibility is Addisons disease. Apart from the skin thing, you get extremely tired and generally have symptoms similar to low thyroid. I would recommend that you ask to get your cortisol level measured to check this - if it is low, your doctor should order follow up tests.
But I think the kideny problems sounds more likely. If you type "skin discoloration kidney disease" into Google you'll find a lot of info.
you are correct on my vit d dose. and i will print this out when i go back to the doc. thank you all for taking the time to answer!!
and a thyroid level of zero means my thyroid has not been working. i am up to 20% function, not sure how they know this from simple weekly blood tests.