Bone Abstracts

Methimazol is an antithyroid drug for treatment of hyperthyroidism. Methimazol inhibits the enzyme thyroperoxidase participating in thyroid hormone synthesis and reduces triiodothyronine (T₃) and thyroxine (T₄) blood concentrations. The study was performed to determine effects of 90-day long oral administration with methimazol on femur properties isolated from male Wistar rats. The first group (n=6) consisted of control rats. The experimental rats (Met group, n=6) received methimazol in 0.05% water solution ad libitum. At 6 months of life, serum concentration of osteocalcin (OC) was determined and right femurs were isolated to measure bone length and weight. Total bone volume (Bvol) and mean volumetric bone mineral density (MvBMD) of femur was determined with a use of quantitative computed tomography (QCT). Using peripheral QCT (XCT Research SA Plus apparatus, Stratec Medizintechnik GmbH, Pforzheim, Germany) and dual-energy X-ray absorptiometry (DEXA; Norland Excell Plus Densitometer, Fort Atkinson, WI, USA), bone mineral content (BMC), and bone mineral density (BMD) of the trabecular and cortical bone were evaluated. Furthermore, trabecular (TBA) and cortical (CBA) bone areas, periosteal (PC) and endosteal (EC) circumferences, axial (AMI) and polar (PMI) moments of inertia, and moment of resistance (SSI) were determined. Final body weight of experimental rats was significantly lowered by 30% when compared to the controls (P=0.01) Serum concentration of OC was significantly decreased in experimental rats (3.06±0.46 ng/ml) when compared to the controls (3.89±0.46 ng/ml; P=0.03). Significantly decreased values of bone weight, length, Bvol, MvBMD, BMC, BMD, TBA, CBA, PC, AIM, PIM, and SSI of femur were found in the experimental rats when compared to the controls (P<0.05). In conclusion, this study showed negative effects of long-term oral administration with methimazol on bone formation process and morphological and densitometric properties of femur. Long-term antithyroid treatment may lead to growth inhibition and development of osteopenia or osteoporosis.