Bone mineral density in premenopausal subclinical and clinical hyperthyroid women

Objective: The aim of this study is to evaluate the effects of subclinicalhyperthyroidism (SH) and clinical hyperthyroidism (H) on bone metabolism, andmineral density (BMD) in premenopausal women.Materials and methods: Sixteen H (31.3±9.5 yrs), 23 SH (33.7±7.3 yrs) and 20 healthy(31.7±8.1 yrs) premenopausal women were enrolled into the study. BMD was assessedby DXA through lumbar vertebrae and femur. Osteocalcin, total alkaline phosphatase(tALP), homocysteine and β-2 microglobulin, hsCRP were assessed in serum samples;and deoxypyridinoline (DPD) and calcium in urinary. The groups were matched fordemographic, anthropometrical parameters; and osteoporotic risk factors.Results: None of the parameters were different between control and SH groups. Serumcalcium, tALP, osteocalcine, β-2 microglobulin and thyroid receptor antibody (TRAb)as well as thyroid hormones, DPD were significantly different in H group than both SHand control groups. BMD was not different either in SH or even H groups than controls.Thyroid hormones (FT3 and FT4) were correlated with osteocalcin (p=0.0001 for bothFT3, FT4), β-2 microglobulin (p=0001; p=0.006 respectively), tALP (p=0.0001 forboth); lumbar vertebrae BMD (p=0.026; p=0.027 respectively) and femoral BMD(p=0.03; p=0.02 respectively). Both osteocalcine and tALP were significantly andnegatively correlated with vertebrael (p=0.004 and p=0.0001 respectively) and femoralBMD (p=0.004 for both). Additionally β-2 microglobulin; as marker of bone resorption,was slightly but significantly higher in H group. hsCRP was neither different withingroups nor correlated with any study parameters. Despite homocysteine was notdifferent within groups; it was significantly correlated with ALP (p=0.0001) and DPD(p=0.001).Conclusions: There is limited and conflicting data about the effects of subclinicalhyperthyroidism on bone turnover in premenopausal period. Despite we could notestablish any difference for bone turnover markers between control group andsubclinical hyperthyroid patients; with tight correlations between thyroid hormones; wecan conclude that SH patients are prone to osteoporosis. The limitation of this study wasthe lack of longitudinal follow up of these patients in long period of time and theawareness of the condition until diagnose. Additionally younger age could possibly thepreventive factor on bone mineral density.