Normo-hormonal primary hyperparathyroidism presenting with recurrent acute pancreatitis

Primary hyperparathyroidism is an endocrine disorder with diverse clinical and biochemical manifestations. Albright classically described the condition as a disease of "stones, bones, groans, and moans." Its clinical spectrum may include recurrent acute pancreatitis secondary to hypercalcemia. Although biochemically the disorder typically presents with elevated serum calcium, reduced serum phosphate, and increased parathyroid hormone (PTH) levels, atypical manifestations are possible. We report the case of a 41-year-old man who presented with recurrent episodes of acute pancreatitis and on evaluation was found to have persistently elevated serum calcium and low serum phosphorus levels with intact PTH (iPTH) concentrations within the laboratory reference range. In the context of hypercalcemia, a normal PTH level was considered inappropriately normal because physiologic feedback would typically suppress PTH secretion. Consequently, normo-hormonal primary hyperparathyroidism (NHpHPT) was suspected, and localization workup undertaken. Dual-phase technetium ^99mTc Sestamibi scintigraphy demonstrated a right inferior parathyroid adenoma, subsequently confirmed by four-dimensional computed tomography (4D-CT). The patient had bilateral renal calculi. Focused right inferior parathyroidectomy resulted in biochemical normalization and marked clinical improvement. This case highlights the heterogeneous manifestations of primary hyperparathyroidism and emphasizes that a normal PTH level in the context of hypercalcemia does not exclude the diagnosis of hyperparathyroidism.