Dose replacement effect of levothyroxine on bone mineral density in premenopausal women with primary hypothyroidism

Abstract

Background and Objective: Patients with hypothyroidism require thyroid hormone replacement. Many studies have shown that bone density reduction is caused by suppressive doses of levothyroxine, but there are contradictory results regarding the effect of levothyroxine replacement dose (non suppressive). The purpose of this study was to investigate the effect of replacement doses of levothyroxine on bone mineral density in premenopausal females with primary hypothyroidism. Materials and methods: In this analytic case - control study, 55 females aged 30 to 50 years with primary hypothyroidism who received levothyroxine for at least two years, with TSH of 0.1 to 4.5 over their follow ups underwent densitometry using DXA method in spine and hip and then were compared with 55 subjects in the control group. Results: The mean differences in bone mineral density and Z-score of total femur zone, neck of femur and lumbar spine zone were significant in control and case groups. There were no significant correlations between the duration and dose and bone density in femur zone (neck and total) and lumbar spine. Likewise, there was no significant correlation between TSH and bone density in total femur zone and lumbar spine; however, the difference was significant in femur neck zone, but not at the level of osteoporosis and osteopenia. Conclusion: This study indicates that taking levothyroxine even with replacement dose (TSH within the normal range) can result in prominent changes in bone density, although it is not clinically significant. é 2015, Zanjan University of Medical Sciences and Health Services. All Rights Reserved.