DECREASED PARATHYROID FUNCTION IN HYPERTHYROIDISM: INTERRELATIONSHIPS BETWEEN SERUM PARATHYROID HORMONE, CALCIUM-PHOSPHORUS METABOLISM AND THYROID FUNCTION

Publisher Website
Google Scholar
Abstract
Serum immunoreactive parathyroid hormone (S-iPTH) was measured together with serum and urinary Ca and P in 45 hyperthyroid patients in order to assess parathyroid function. Serum Ca and P were increased and positively correlated to the degree of hyperthyroidism. The prevalence of hypercalcemia was 51.1% using serum Ca values corrected for individual variations in serum albumin concentration compared to 15.6% using the uncorrected Ca values. S-iPTH was decreased and inversely correlated to serum Ca (corrected). Subnormal levels of S-iPTH were found in 28.9% of the patients. Urinary excretion of Ca and P was increased and positively correlated to the degree of hyperthyroidism. The tubular reabsorption of Ca (TRCa%) was decreased, positively correlated to S-iPTH and inversely correlated to serum Ca. Increased mobilization of bone mineral in hyperthyroidism is probably responsible for the elevated serum levels and increased urinary excretion of Ca and P and for decreased parathyroid function.