[The influence of treatment with substitutive or suppressive doses of thyroxine on biochemical bone turnover markers].

Purpose: Thyroid hormones belong to essential regulators of growth and remodelling of bones. The development of modern radioimmunological and immunoenzymatic methods opened the way to studies on the influence of exogenous thyroxine on the metabolism of osseous tissue. The activity of osteoblasts and the osteoclast ratio is a measure of the process termed "bone turnover" which can be assessed by determining concentrations of enzymes and bone matrix proteins in serum. The aim of this study was to evaluate the influence of a twelve-month regimen with substitutive or suppressive doses of thyroxine on bone alkaline phosphatase (BAP) concentrations in serum and deoxypyridoline (DPR) concentrations in the urine of women with hypothyroidism or with simple goitre.
Material and Methods: We enrolled 26 women with not-treated hypothyroidism (Group I) and 41 with not-treated simple goitre (group II). The age of the patients ranged from 29 to 66 years. Patients were qualified for treatment with substitutive (hypothyroidism) or suppressive (goitre) doses of thyroxine. Each group was divided into two subgroups: IA--15 premenopausal patients with hypothyroidism (mean age 41.53 +/- 1.39 years); IB--11 postmenopausal patients with hypothyroidism (mean age 53.18 +/- 1.66 years); IIA--24 premenopausal patients with simple goitre (mean age 39.71 +/- 0.98 years); IIB--17 postmenopausal patients with simple goitre (mean age 53.82 +/- 1.35 years). Evaluations of bone turnover markers in serum (BAP) and in twenty-four hour urine collection (DPR) and serum concentrations of TSH, FT3 and FT4 were carried out prior to treatment and after 1, 3, 6, 9 and 12 months ofthyroxine administration.
Results: Bone turnover markers increased during treatment with substitutive or suppressive doses of thyroxine, especially in postmenopausal women.
Conclusions: 1. Treatment with substitutive or suppressive doses of thyroxine stimulates osteogenic and osteoclastic processes in pre- and postmenopausal women. 2. Suppressive doses of thyroxine are more potent in increasing bone turnover than substitutive doses. 3. The osteoclastic process is more intense in postmenopausal women on substitutive or suppressive doses of thyroxine.