Milk alkali syndrome. Does it exist and can it be differentiated from primary hyperparathyroidism?

Four patients with milk-alkali syndrome (MAS) presented with many of the characteristics of primary hyperparathyroidism including hypercalcemia, low or normal serum phosphorus levels, normal or increased urinary calcium levels, and inappropriately high or elevated serum parathyroid hormone levels. These laboratory findings differ from those classically described in MAS, i.e., hypercalcemia without hypercalciuria and a normal or high plasma phosphate level. Because the serum calcium level failed to return to normal after two weeks of hydration and a low calcium diet, and because of the inability to distinguish this syndrome from primary hyperparathyroidism, two of the four patients underwent neck exploration. Four normal parathyroid glands were histologically proven in each, and at autopsy in a third patient, there was no evidence of parathyroid hyperplasia or adenoma. Hypercalcemia eventually resolved in all patients with a low-calcium diet for as long as six months. Of the several features of MAS, hypercalcemia, alkalosis in the presence of azotemia, a history of increased calcium and alkali intake, and a response to dietary calcium restriction are helpful in differentiating this syndrome from primary hyperparathyroidism. Laboratory tests in patients with MAS may be confusing and the return to normocalcemia in response to a calcium deficient diet may be delayed.