Since so many of us with osteo also have thyroid disease, I thought this might be helpful to post. A few others here, like me, have had a hard time increasing our vitamin D intake for bone health as it causes a "hyper" feel, I recently found that this is because it makes the thyroid gland work more efficiently -- often converting T4 into T3 at a higher rate---thus the hyper feel.
On another thyroid blog there was a discussion about this same hyper experience with D occurring for others and all they had to do was lower their thyroid medication a little bit and then could resume taking D. Apparently as in other autoimmmune diseases, the D makes your thyroid work better. I had been lowering my D intake instead not realizing it was affecting my thyroid, and now since lowering my synthroid a little bit, I can take higher amounts of D and still have normal thyroid levels. Probably will still have to experiment for a while to get optimal balance between the two.
An endocrinologist jumped into one of the discussions and said that he always had a lot of patients who had to lower their thyroid meds during the summer and raise them back up in the winter, so clearly that was the vitamin D in the summer making their thyroid work better.
Hope this helps, Santa Fe