Serum calcium in thyroid disease

Thyroid hormones are believed to influence calcium metabolism. In the prese nt prospective study we investigated the influence of various thyroid disea ses on serum calcium levels. In addition to screening for thyroid diseases we measured serum calcium concentrations (S-Ca) in individuals who came to our outpatient service for thyroid diseases from 1992 to 1998. 13,387 perso ns, among them 9017 patients with thyroid diseases and 4370 persons without thyroid dysfunction, were studied. S-Ca was found to be higher in patients with hyperthyroidism (2.36 +/- 0.11 mmol/L n = 1201, p < 0.05) than in those with subclinical hyperthyroidism (2.33 +/- 0.11 mmol/L, n = 494), with euthyroid-goiter (2.32 +/- 0.10 mmol/ l, n = 5599), with hypothyroidism (2.31 +/- 0.11 mmol/L, 344), with subclin ical hypothyroidism (2.32 +/- 0.10 mmol/L, n = 1290) and in healthy persons (2.31 rt: 0.11 mmol/L, n = 4370). 173/13,387 persons had serum calcium lev els < 2.1 mmol/L, among them 31 patients with hypoparathyroidism after stru mectomy (31/592) and 2 patients with primary hypoparathyroidism. 106/13,387 persons showed a S-Ca of > 2.6 mmol/L, which in 30 cases was due to primar y hyperparathyroidism. Of 55 persons with S-Ca of >2.6mmol/L and without an y other reason for hypercalcaemia, 31 were found to be in a hyperthyroid st ate. In conclusion, a clinically not relevant influence on S-Ca was demonstrated in patients with hyperthyroidism as compared with other thyroid diseases a nd individuals with no thyroid diseases. Measurement of S-Ca in every patie nt being referred to a thyroid outpatient department is recommended because of the frequent occurrence of postoperative hypoparathyroidism and primary hyperparathyroidism in this setting.