Endocrine Abstracts

Introduction: Primary hyperparathyroidism (PHPT) is the most common cause of hypercalcemia, most cases with parathyroid adenoma as the underlying pathology. However, when blood and urine calcium levels and PTH are higher than normal in PHPT, t’s important to suspect an ectopic PTH secretion or a parathyroid carcinoma. Intrathyroidal parathyroid cysts are extremely rare cause of severe PHPT.

Clinical case: A 36-year-old male presented with dizziness and weakness for several weeks. Osmotic polyuria and nocturia with thirst were also impairing his quality of life. He had no history of renal lithiasis or hypertension. Biochemical features were suggestive of PHPT (Ca²:12.9 mg/dl; iPTH:>300 pg/ml; Ca_u:11.5mg/kg/24 h). Physical exploration shows normal thyroid palpation and there were no lipomas or facial angiofibromas. BMD was reduced and skull X-ray revealed a brown tumor. US also showed bilateral renal microlithiasis. No family background of MEN 1. CT showed a right thyroid nodule and a possible left parathyroid adenoma but Tc99m sestamibi scintigraphy revealed radio tracer uptake in the right lobe of thyroid. In ultrasonography no parathyroid lesions were located, but a solid-cystic nodule in the right lobe was observed. US-FNA of the thyroid nodule followed by cyst iPTH measurement (2,170,000 pg/ml) confirmed intrathyroidal parathyroid gland. Treatment with 30 mg of cinacalcet was initiated, but without calcium decrease until 210 mg daily dose. After sharing our clinical suspicion with the surgeon, an hemithyroidectomy was performed, checking that PTH dropped to normal levels. Twenty-four hours after surgery, the patient started with paresthesias and positive Trousseau sign, PTH level was of 5 pg/ml with normocalcemia. After resolution of symptoms with IV calcium, oral calcitriol and calcium carbonated were initiated. Two weeks after surgery both medications were stopped without symptoms at all.

Conclusions: 1. Intrathyroidal parathyroid cystic adenoma is an extremely rare cause of PHPT.

2. FNA-iPTH is a helpful tool to make an accurate diagnosis when an intrathyroidal parathyroid adenoma is suspected.

3. Elevated levels of PTH and bone disease before parathyroidectomy, are risk factors for hungry bone syndrome.