INTRODUCTION: Indiscriminate serum calcium measurement may lead to the identification of asymptomatic patients with hypercalcaemia, which is caused mostly by primary hyperparathyroidism. OBJECTIVE: To discuss the frequency of hypercalcaemia and the type of assessment of this condition in an outpatient population, with emphasis on the investigation of primary hyperparathyroidism. MATERIAL AND METHODS: In a prospective study 1,049 subjects (age range: 40 to 60 years old) underwent serum calcium and albumin determination and the corrected calcium values were calculated. When there was a rise in the corrected calcium level, ionized calcium, phosphate, parathyroid hormone (PTH) and urinary calcium were measured. RESULTS: The average age was 49.7 ± 13.7 years old, and 188 subjects (17.9%) had elevated corrected calcium levels. Among these, 90 patients underwent the second investigation and 19 (2%) remained hypercalcemic. Ionized calcium levels (average: 1.2 ± 0.01 mmol/L) were normal in all subjects. Urinary calcium was 185.8 ± 111.8 mg/24 hours. PTH levels (average: 46 ± 11.8 pg/mL) were elevated in three subjects whose parathyroid scintigraphies were normal. DISCUSSION: The fall in the frequency of hypercalcaemia based on corrected serum calcium levels and mostly after determination of serum ionized calcium suggests that determinations of serum free calcium are a better screening test. No subject was diagnosed with hyperparathyroidism, what suggests an uneven distribution of the disease in different populations. CONCLUSION: Routine serum calcium determinations in asymptomatic patients must be questioned. When serum calcium determination is thought necessary, ionized calcium levels should be favored.
Hypercalcemia; Hyperparathyroidism; Serum calcium