Abstract
The purpose of the study was to observe changes in the skeletal system of rats with subclinical hypothyroidism (SCH) and to determine whether L-thyroxine (L-T4) administration suppresses those changes. Sixty male Wistar rats were randomly divided into control, SCH, and SCH+T4 groups. SCH was induced in rats by administration of methimazole (MMI), and rats in the SCH+T4 group were treated with L-T4 after 45 days of MMI administration. The SCH group had higher thyroid-stimulating hormone (TSH) level than the control and SCH+T4 groups. There were no differences in serum thyroid hormone (FT4 and FT3) levels among the three groups. Bone mineral density; serum levels of BALP and TRACP-5b, two bone metabolic markers; and the biomechanical properties of the femurs were lower in the SCH group than in the control group. After L-T4 treatment, serum BALP and TRACP-5b levels and the femur biomechanical properties were higher in the SCH+T4 than the SCH group. Histopathological examination revealed damage to the structure of the femur trabecular bone network in rats with SCH, and L-T4 treatment improved this condition to some extent. These findings demonstrate that L-T4 treatment ameliorates the destructive effects of SCH on the skeletal system in rats.
Highlights
Subclinical hypothyroidism (SCH) is an increased concentration of thyroid-stimulating hormone (TSH) with a normal level of thyroid hormone [1]
These studies established the hypothyroid rat model, so we reduced the dose by fivefold to establish the subclinical hypothyroidism (SCH) rat model
After 45 days of mg/kg/d of methimazole (MMI) administration, we detected increased levels of thyroidstimulating hormone (TSH) (P
Summary
Subclinical hypothyroidism (SCH) is an increased concentration of thyroid-stimulating hormone (TSH) with a normal level of thyroid hormone [1]. SCH, the mildest form of hypothyroidism, lacks the specific signs and symptoms of clinical hypothyroidism [2]. The prevalence of SCH is between 4% and 20% in the general population and higher in women than in men, ranging from 11% to 17% in community-dwelling elderly populations [3,4,5,6]. SCH progresses to overt hypothyroidism in approximately 2% to 5% of cases annually [7]. Overt thyroid dysfunction is associated with decreased bone mineral density (BMD) and increased risk of fracture [8, 9]. Thyroid hormone is a factor in bone remodeling that acts directly or indirectly on bone cells, influencing bone resorption and bone formation [10, 11]
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