Endocrine Abstracts

After thyroidectomy (Tx) and RAI therapy, patients with diffentiated thyroid cancer are treated with levo-thyroxine to suppress TSH levels. Whether hyperthyroxinemia causes osteoporosis is debated. The aim of this study was to evaluate bone mineral density (BMD) and the fracture risk assessment tool (FRAX) in DTC women. FRAX calculates the 10-year probability of hip fracture (HF) and major osteoporotic fracture (MOF) in subjects aged >40. 46 women with DTC diagnosed and treated (Tx 96%, RAI 72%) at the age of 52.4±10.3 years were studied. L-T₄ was started 58 mts before Tx for goiter in 15% of patients. Baseline BMD measured by DXA of the lumbar spine and FRAX score calculated on femoral neck BMD were evaluated 2.5 years after diagnosis. The age at this time was 56.2±8.0 years and 76% of patients were postmenopausal. BMD and FRAX evaluations were repeated after 5.5 years. Neck sonography and thyroglobulin levels indicated a disease-free condition at each experimental time. L-T₄ dosages were 809±229 μg/week and 790±153 μg/week at the baseline and 2nd evaluation respectively. Results are reported as means±s.d. (medians in brackets) (Table 1).

Adequate TSH levels under moderate hyperthyroxinemia were more often observed on follow-up than on baseline evaluation, without significant changes in BMD. Significant changes in FRAX were found from the baseline to the 2nd evaluation, with the probability of HF increasing more than that of MOF. A significant inverse correlation (P<0.01) emerged between L-T₄ dosage and HF/MOF probability, both at the baseline and the 2nd evaluation, while a further slightly significant inverse correlation (P=0.05) was found between F-T₄ levels and HF/MOF probability only at the 2nd evaluation. In conclusion, FRAX increase seems to be an age-related multi-factorial phenomenon. In DTC women, lumbar BMD does not change as much as FRAX. The absence of positive correlations between L-T₄ dosage, length of therapy or F-T₄ levels and FRAX does not allow us to attribute an increased fracture risk to DTC women with well-controlled disease. A larger population of DTC patients and a longer period of observation may yield more conclusive data.