Reduced bone mass detected by bone quantitative ultrasonometry and DEXA in pre- and postmenopausal women with endogenous subclinical hyperthyroidism.

Background: Although overt hyperthyroidism is a well known cause of bone loss, systemic effects of subclinical hyperthyroidism (SH) are still a matter of debate.

Objective: The aim of this cross-sectional study was to evaluate the effect of endogenous SH on bone in relation to the menopausal status.

Methods: Bone mass and turnover were assessed in a group of 60 patients with endogenous SH due to multinodular goitre; 30 of them were premenopausal and 30 early postmenopausal (mean age, 40.9 +/- 7.3 and 57.7 +/- 6.75, respectively). Sixty healthy women matched for age-, BMI- and menopausal status served as controls. Three different skeletal sites were evaluated using two different techniques: lumbar spine and femoral neck were assessed by DEXA whereas the proximal phalanges were evaluated by quantitative ultrasonometry (QUS), measuring the amplitude-dependent speed of sound (Ad-SoS). Serum osteocalcin and urinary deoxypyridinoline (DPD) were also determined as markers of bone turnover.

Results: A significant decrease was found in femoral BMD (P < 0.05) and phalangeal Ad-SoS (P < 0.001) in pre- and postmenopausal patients compared to controls, being greater in those postmenopausal. Lumbar BMD was decreased only in postmenopausal patients (P < 0.05). Bone turnover markers were higher in patients than in controls and in post- than in the premenopausal ones. A significant negative correlation was found between femoral BMD, Ad-SoS and serum free T3 levels, the latter considered a marker of disease activity.

Conclusions: A significant increase in bone turnover markers and a decrease in bone mass was found in women affected by endogenous SH, being greater in early postmenopausal patients. Cortical rich bone was mainly affected. Both QUS and the conventional DEXA technique were equally able to determine bone density decrease related to mild thyroid hormone excess and sexual hormone decrease.