Prevalence of primary hyperparathyroidism in 13387 patients with thyroid diseases, newly diagnosed by screening of serum calcium

Primary Hyperparathyroidism (PHP) often goes unrecognised. Evidence of the influence of thyroid diseases on parathyroid activity exists. In order to d etermine the prevalence of primary hyperparstthyroidism (PHP) in patients w ith thyroid diseases, a series of patients referred to an outpatient depart ment for patients with thyroid diseases were examined for additional PHP. In addition to screening for thyroid diseases, serum calcium concentration (S-Ca) was measured in a series of persons who came to our outpatients' ser vice for patients with thyroid diseases during the period 1992 to 1998. 133 87 persons, median age 48 y, m = 2367, f = 11020, among them 9017 patients with thyroid diseases and 4370 persons without thyroid dysfunction, were st udied. In patients with S-Ca outside the normal range, further diagnostic t ests relating to PHP were performed. 106/13387 persons showed S-Ca greater than or equal to 2.6 mmol/L, in 31 ca ses due to PHP. In comparison to persons without thyroid diseases, the occu rrence of PHP was significantly higher in patients with thyroid diseases (4 /4370 = 0.09% vs. 26/9017 = 0.29%). Furthermore, 2 patients with normal S-C a were diagnosed as having PHP in addition to another endocrine disease (ac romegaly, multiple endocrine neoplasia type IIa, resp.). 31 of the 54 perso ns with S-Ca > 2.6 mmol/L and who showed no other reasons for hypercalcaemi a were found to be in a hyperthyroid state. The prevalence of PHP was signi ficantly higher in patients with euthyroid goitre (p < 0.05) and in patient s with thyroid carcinoma (p = 0.01) as compared to other persons with thyro id diseases. The groups of patients did not differ with regard to age. Howe ver, patients without thyroid diseases were significantly younger (median a ge 38y). Above the age of 50, the prevalence of PHP became higher in patien ts with euthyroid goitre or thyroid carcinoma than in those with a healthy thyroid gland. In contrast, in persons of under 50 y, there was no differen ce between these groups. The percentage of males with PHP was higher than i n the total population studied (30% vs. 21.5%). In conclusion, a high occurence of PHP could be demonstrated in patients wi th thyroid diseases (0.29%) as compared to persons without thyroid dysfunct ion (0.09%), the highest prevalence being in patients with thyroid carcinom a. A clinically not relevant influence of thyroid function on S-Ca was seen in some patients with hyperthyroidism. Determination of S-Ca is recommende d for each patient referred to a thyroid outpatients' department because of the high number of PHP cases in this context.