Ionized and total serum calcium and parathyroid hormone in hyperthyroidism

Ann Intern Med. 1976 Jun;84(6):668-71. doi: 10.7326/0003-4819-84-6-668.


Total and ionized calcium concentrations as well as parathyroid hormone levels were measured in a group of hyperthyroid persons. Ionized and total calcium levels were elevated in 21 of 45 (47%) and in 12 of 45 (27%) thyrotoxic patients, respectively. Mean ionized and total calcium levels were higher in these 45 patients than in normal persons. Using two different radioimmunoassay systems for a total of 44 determinations, mean parathyroid hormone levels were lower in thyrotoxic patients than in subjects with proved hyperparathyroidism. These data suggest that [1] elevations of both ionized and total calcium concentrations occur frequently in thyrotoxic patients; [2] ionized calcium concentrations may be elevated in a higher percentage of hyperthyroid subjects than are total calcium concentrations; and [3] the hypercalcemia associated with thyrotoxicosis is not associated with elevated parathyroid hormone levels.

MeSH terms

  • Calcium / blood*
  • Female
  • Humans
  • Hyperthyroidism / blood*
  • Immune Sera
  • Ions
  • Parathyroid Hormone / blood*
  • Pregnancy


  • Immune Sera
  • Ions
  • Parathyroid Hormone
  • Calcium