The association between the IGF-I axis, thyroid hormones and cortical bone in patients with mild primary hyperparathyroidism.

Objectives: Primary hyperparathyroidism (PHPT) is associated with low bone mineral density (BMD) and increased risk of osteoporotic fractures. This study investigated whether the IGF-I axis and thyroid hormones are associated with BMD and osteoporotic fractures before and after parathyroidectomy (PTX).

Materials And Methods: Forty-five patients with mild PHPT were examined before and 1 year after PTX. Circulating concentrations of IGF-1, IGFBP-3, and thyroid hormones were measured and related to BMD in hip and lumbar (L:2-L:4) spine.

Results: Serum IGFBP-3 concentration decreased 1 year after PTX (p < 0.01), whereas serum IGF-1 and thyroid hormone concentrations were unchanged. Serum IGF1 concentration correlated positively with IGFBP-3 concentration (p < 0.0001) and BMD in the femoral neck (p < 0.05), both pre- and postoperatively. Serum IGFBP-3 concentration correlated positively with BMD in the femoral neck postoperatively (p < 0.05). Serum TSH correlated positively, and free thyroxine (T4) negatively, with all measures of hip BMD at baseline. Patients suffering from previous osteoporotic fractures before inclusion had lower serum TSH concentration compared to patients without fractures (p < 0.01).

Conclusion: Serum IGFBP-3 concentration decreased after successful PTX in patients with mild PHPT, while serum IGF1 and thyroid hormone concentrations were unchanged. Both the IGF-I axis and thyroid hormones associated with cortical bone as serum IGF-1 and IGFBP-3 concentrations correlated positively, and free T4 negatively with hip BMD. Moreover, serum TSH concentration was reduced in patients with previous osteoporotic fractures.