Prevalence and risk factors for primary hyperparathyroidism in hyperthyroid patients

BACKGROUND: Coexistence of hyperthyroidism and primary hyperparathyroidism may be more prevalent than previously recognized. We report 13 cases of concomitant occurrence of both diseases to estimate their combined prevalence and its factors. METHODS: Ninety-six unselected patients admitted for elective hyperthyroidism surgery were retrospectively included. Eighty-three patients were initially seen for hyperthyroidism with normocalcemia (group 1), and 13 patients were initially seen for hyperthyroidism with associated primary hyperparathyroidism (group 2). Patients' characteristics, examinations, and pathology reports were reviewed. Risk factors were identified using a logistic regression model. RESULTS: The prevalence of concomitant hyperparathyroidism was 13.5%. No patients manifested hypercalcemia in the absence of organic parathyroid disease. Eleven patients had a parathyroid adenoma, and two patients had parathyroid hyperplasia. Group 2 patients were older (median 61 vs 43 years, p = .006). Thyroid-stimulating hormone levels were more depressed in group 2 (median 0.01 vs 0.032 UI/L, p = .034). On multivariate analysis, age was the unique factor significantly different between groups (odds ratio, 1.05; 95% confidence interval, 1.008-1.098; p = .020). CONCLUSIONS: Hypercalcemia in patients with hyperthyroidism, particularly older patients, should warrant a thorough investigation for concomitant primary hyperparathyroidism that would dictate a combined thyroidectomy and parathyroidectomy.