The parathyroid glands are the main regulator of plasma calcium and have a direct influence on the digestive tract. Parathyroid disturbances often result in unknown long-standing symptoms. The main manifestation of hypoparathyroidism is steatorrhea due to a deficit in exocrine pancreas secretion. The association with celiac sprue may contribute to malabsorption. Hyperparathyroidism causes smooth-muscle atony, with upper and lower gastrointestinal symptoms such as nausea, heartburn and constipation. Hyperparathyroidism and peptic ulcer were strongly linked before the advent of proton pump inhibitors. Nowadays, this association remains likely only in the particular context of multiple endocrine neoplasia type 1/Zollinger-Ellison syndrome. In contrast to chronic pancreatitis, acute pancreatitis due to primary hyperparathyroidism is one of the most studied topics. The causative effect of high calcium level is confirmed and the distinction from secondary hyperparathyroidism is mandatory. The digestive manifestations of parathyroid malfunction are often overlooked and serum calcium level must be included in the routine workup for abdominal symptoms.

This review discusses gastrointestinal manifestations of parathyroid diseases. Parathyroid hormone is the primary regulator of calcium physiology. Hypoparathyroidism can be idiopathic, hereditary, or secondary to surgery in the neck. Hyperparathyroidism is usually from adenomas or hyperplasia. Hypoparathyroidism is associated with steatorrhea that may improve with medium-chain triglycerides, correction of the hypoparathyroidism, or administration of vitamin D. Hyperparathyroidism results in constipation because of reduction in neuromuscular excitability by high calcium levels. According to old literature, the incidence of peptic ulcer disease (PUD) in patients with hyperparathyroidism is 9% compared with autopsy rates of 4% to 5%. Any association is difficult to prove today, as hyperparathyroidism is usually mild due to early detection of cases through routine automated measurements of calcium. In addition, PUD is less prevalent now than before the advent of proton pump inhibitors. The presence of ulcers or ulcer symptoms may correct in some patients after parathyroidectomy, suggesting an association. The incidence of pancreatitis in patients with primary hyperparathyroidism ranges from 1.5% to 12% and may be because of the hypercalcemia. Complicating the issue is secondary hyperparathyroidism in response to hypocalcemia from pancreatitis. Pancreatitis may improve in some individuals after parathyroidectomy. Pancreatitis may follow parathyroid surgery because of an acute rise in calcium levels with manipulation of the parathyroid glands or to a blunted response of calcitonin-producing cells from fatigue. Parathyroid diseases have a few distinct effects on the gut: steatorrhea in hypoparathyroidism, and constipation, PUD, and pancreatitis in hyperparathyroidism.

Two boys with idiopathic hypoparathyroidism had extensive studies of gastrointestinal function during hypocalcemia accompanied by steatorrhea. No evidence of generalized gastrointestinal moniliasis or abnormal mucosal structure or function was observed. Studies of pancreatic function and bile salt metabolism during hypocalcemia demonstrated deficient meal-stimulated intraluminal pancreatic enzyme concentrations in both subjects and reduced bile salt concentrations in one subject. However, following stimulation with exogenous octapeptide of cholecystokinin, intraluminal pancreatic enzyme and bile salt concentrations were normal in both. Cholic acid pool sizes were markedly increased in both subjects during hypocalcemia (9 and 12 times larger than during normocalcemia) and cholic acid turnover was reduced during hypocalcemia in one subject. Our findings suggest that during hypocalcemia, insufficient endogenous cholecystokinin is released by the duodenal mucosa during a meal stimulus to stimulate normal gallbladder contraction and pancreatic enzyme secretion.

Our study suggests that coexisting celiac sprue is one of the mechanisms responsible for the malabsorption associated with idiopathic hypoparathyroidism. Celiac sprue is relatively common, and this association could occur by coincidence. Alternately there may be shared determinants of susceptibility or perhaps a direct immunological relationship. In such patients, both gluten-free diet and correction of the hypoparathyroid state may be necessary to correct malabsorption. In our literature survey, this is the first case in which celiac sprue associated with idiopathic hypoparathyroidism was documented. The importance of intestinal biopsy in evaluating malabsorption in patients with idiopathic hypoparathyroidism is emphasized.