Bone Abstracts

Background: Patients with differentiated thyroid cancer (DTC) are treated with L-thyroxine (L-T₄) in relatively hight doses to suppress endogenous TSH levels. Very long-term effect of thyroid hormones supplementation on bone are controversial.

Objetive: To study the possible negative effects on bone mineral density (BMD) and bone markers in DTC patients followed in our center.

Methods: A 46 postmenopausal women (age 62.85±11.29 years) with DCT on TSH suppressive treatment for 27.72±4.04 years were classified at baseline in: Group 1=premenopausal and Group 2=postmenopausal. BMD was measured by DXA (Hologic QDR 1000) at baseline (year 1992) and at the present time at lumbar spine (LS),total hip (TH), femoral neck (FN) and ultradistal radius (UDR). Serum bone turnover markers (β-CTX and osteocalcin) and calcitropic hormones (PTH and 25OH vitaminD) were measured.

Results: At the 25 years follow-up study: Group 1: n=27, age 56.3±8.4 and Group 2: n=19, age 72.1±7.8 years. Compared with baseline, we found a statistically significant decrease in BMD at LS (P=0.000) and FN (P=0.000) in Group 1. No significant changes were found in Group 2. Percentage of BMD change were: Group 1: LS −6.23±11%; FN −8±12%; TH 3.2±12%; and UDR 2.7±7.7%.Group 2: LS 3.6±19%; FN −8.5±12.2%; TH −5±16.8%; and UDR 7.5±3.5%. At the second DXA, group two had lower BMD than group one at all localizations (at TH and UD statistically significant). Osteoporotic women were 39.1% (total), 22.2% (Group 1) and 63.2% (Group 2). No correlation was found between BMD and TSH, L-T₄ dose, PTH, β-CTX or vitamin D. Only osteocalcin showed a negative correlation with BMD at UDR (r=−0.58, P<0.01) and TH (r=−0.51, P0.04) in Group 1.

Conclusion: Very long-term L-T₄ suppressive therapy in women with DTC does not induce severe bone loss. Patients that began therapy in postmenopausal status had lower BMD compared to premenopausal women at the end of the study.