Endocrine Abstracts

JOINT2338

Sporadic primary hyperparathyroidism (PHPT) is usually caused by a single-gland adenoma, which on histopathology has a marked cellularity with a reduced amount of stromal fat. A 72-year-old woman was referred for evaluation of PHPT. Laboratory tests showed hypercalcemia (2.69 mmol/l, normal range 2.20-2.55) and elevated parathyroid hormone (14.40 pmol/l, normal range 1.58-6.03). She had been treated with alendronate for osteoporosis of the distal third of the radius, fulfilling an indication for parathyroidectomy in asymptomatic PHPT. Ultrasonography showed a 0.2 ml oval hypoechoic nodule inferior to the right lobe of the thyroid, which was confirmed by MIBI scintigraphy. However, an enlarged parathyroid below the right thyroid lobe was not found during the parathyroidectomy. The surgeon therefore extended the operation to include a right exploration and found an enlarged parathyroid behind the middle part of the right thyroid lobe. Although the blood calcium level normalized on the first postoperative day, two weeks after surgery it was at the same level as before the parathyroidectomy, consistent with persistent PHPT. The right upper parathyroid gland was initially described as an enlarged but normal parathyroid gland (13x5x7mm). After the second reading it was corrected to a parathyroid lipoadenoma due to the abnormal size and clinical context of PHPT. The patient has stable mild hypercalcemia with isolated osteoporosis in the radius. Reoperation for persistent PHPT is under consideration, the conservative approach may also be acceptable. Parathyroid lipoadenoma is a rare histological finding in PHPT with a prevalence of 0.2-1.0%. The presence of stromal fat in lipoadenoma resembles a normal parathyroid gland, which may confuse not only the pathology but also parathyroid imaging. While typical parathyroid adenomas are hypoechoic on ultrasound, lipoadenomas are hyperechoic due to the fat-rich content, which may contribute to the failure of both preoperative ultrasonography and scintigraphy. Both methods correctly localized only one of two pathological parathyroid glands in the present case, highlighting the fact that multiglandular PHPT is often associated with equivocal parathyroid imaging and a high rate of surgical failure. Supported by MH CZ - DRO (Institute of Endocrinology - EÚ, 00023761)