Low TSH triggers bone loss: Fact or fiction?

We reported that thyroid-stimulating hormone (TSH) has direct effects on bone by demonstrating that TSH receptor (TSHR) haploinsufficient mice with normal circulating thyroid hormone levels have osteoporosis and focal osteosclerosis (1). We also found an abundant expression of TSHRs on both osteoclast and osteoblast precursors, and showed that recombinant TSH negatively regulates both osteoclastic bone resorption and osteoblastic bone formation (1). We suggest that a suppressed TSH level contributes to the bone loss in thyroid disease.