Transient hypoparathyroidism induced by synthetic human parathyroid hormone-(1-34) treatment

Daily injections of low doses of a synthetic fragment of human PTH [hPTH-(1-34) have increased iliac trabecular bone volume when used in the treatment of osteoporosis. In approximately 50 patients no major side-effects had occurred. However, during daily sc 100-micrograms injections of the peptide, one patient repeatedly developed parathyroid hypofunction which resolved each time treatment was stopped. Specific immunoglobulin G (IgG) antibodies binding [125I]hPTH-(1-34) were identified in the patient's serum, and positive immunohistochemical reactions were obtained when bovine parathyroid sections were exposed to the patient's IgG. After adsorption with PTH, the patient's IgG, free of anti-PTH antibodies, reacted with renal cell membranes, as demonstrated by indirect immunofluorescence and blocked renal PTH-dependent adenylate-cyclase activation in vitro. These results support the hypothesis that anti-PTH receptor as well as anti-PTH antibodies were generated during hPTH-(1-34) treatment, which led to the development of hypoparathyroidism when their titers were high.