When someone has an overactive thyroid, their high alkaline phosphatase levels are usually because of faster bone turnover, not liver problems — thyroid hormones speed up how bones break down and rebuild.

The study shows that in women with overactive thyroids, bone-building cells are more active, which raises a bone-related enzyme in the blood—supporting the idea that this increase is due to bone changes, not liver problems.

The study shows that thyroid hormones directly turn on bone cells to make more of an enzyme called alkaline phosphatase, which supports the idea that high levels in hyperthyroidism come from bone, not the liver.

The study looks at people taking high doses of thyroid hormone and finds their bones are turning over faster, which supports the idea that high thyroid levels increase bone activity and can raise certain bone-related enzymes in the blood.