Effect of combined treatment with calcitonin on bone densitometry of patients with treated hypothyroidism

INTRODUCTION: Thyroid hormones (TH) may affect bone metabolism and turnover, inducing a loss of bone mass among hyperthyroid and in hypothyroid patients under hormone replacement treatment. Thyroid dysfunction leads to changes in the dynamics of parathyroid hormone (PTH) and calcitonin (CT) secretion. OBJECTIVE: The objective of the study was to determine the usefulness of CT as adjuvant therapy in the prevention of bone loss during the treatment of hypothyroidism. MATERIAL AND METHODS: We studied 16 female patients with recently diagnosed primary hypothyroidism, divided into two groups: group G1 (n=8) submitted to treatment with thyroxine (L-T4), and Group 2 (n=8) that, in addition to being treated with L-T4, received a nasal CT spray. All patients were submitted to determination of TSH, free T4, bone mineral densitometry (BMD) and total bone calcium (TBC) at the time of diagnosis, after 6 to 9 months of treatment, and after 12 months of treatment. RESULTS: No statistical significant differences were detected in either group between the total BMD values obtained for the femur and lumbar spine before and after treatment. However, group G1 presented a statistical significant TBC loss after 12 months of treatment compared to initial values. In contrast, no TBC loss was observed in the group treated with LT-4 in combination with CT, a fact that may suggest that CT was responsible for the lower bone reabsorption during treatment of hypothyroidism.

Development and clinical application of an immunoflurometric assay for intact parathyroid hormone

Parathyroid hormone (PTH) is a linear peptide of 84 amino acids that is found in serum mainly in the form of carboxyl-terminal fragments. The biological activity of PTH depends on the presence of the amino-terminal portion and in circulation is limited to the intact molecule. We describe an immunmofluorometric assay for the measurement of PTH-(1-84) based on a chicken egg yolk-derived amino-terminal antibody bound to microtiter plates by an anti-chicken Ig monoclonal antibody. As tracer antibody we employed a Europium-labelled carboxyl-terminal specific monoclonal antibody produced from a mouse immunized with hPTH-(53-84)-BSA conjugate. The assayincluded an initial overnight incubation of the sample and the solid phase-bound amino-terminal antibody, followed by washing and addition of the tracer antibody, and an additional two hours of incubation prior to fluorescence reading. The least-detectable dose was in the order of 2.5 pg/.ml and preliminary studies in 40 normal adults showed values in the range of 4 to 70 pg/ml; fo 12 patients with surgery-proven primary hyperparathyroidism values ranged from 109 to 743 pg/ml and for 34 patients with humoral hypercalcemia of malignancy from 2.5 to 66 pg/ml. We conclude that this assay, with its increased sensitivity and specificity, will be a valuable tool in the study of PTH secretion in normal and pathological situations