A Case of Primary Hyperparathyroidism Caused By Parathyroid Adenoma of Water-Clear Cell Type

Program: Abstracts - Orals, Poster Previews, and Posters
Session: FRI 368-390-Metabolic Bone Disease Case Reports (posters)
Clinical
Friday, April 1, 2016: 1:15 PM-3:15 PM
Exhibit/Poster Hall (BCEC)

Poster Board FRI 375
Masaya Osawa*, Masuomi Tomita, Takeshi Katsuki, Yoichi Oikawa and Akira Shimada
Saiseikai central hospital, Japan
Background:Although primary hyperparathyroidism (PHP) is generally a common endocrine disorder, the incidence rate in Japan is lower and 5 cases per 100 thousand person-years. PHP is classified into three categories; i.e., adenoma, hyperplasia and carcinoma, and caused most commonly by adenoma. Parathyroid adenomas are mainly composed of chief cell or mixed cell type, whereas oxyphil cell type is less common. Meanwhile, parathyroid adenoma of water-clear cell type is a very rare cause of primary hyperparathyroidism.

Clinical case:A 57-year old female with a history of excised right thyroid (teratoma) and fracture of right knee was noted to have normocalcemia (Ca 8.9 mg/dl, n<10.2 mg/dl) in spite of increased intact parathyroid hormone (iPTH) level of 224 pg/ml in 2011. Because parathyroid tumor could not be detected by ultrasonography at that time, she was followed without therapy. Two years later, hypercalcemia (Ca 13.6 mg/dl) and increased iPTH level (956 pg/ml, n<65 pg/ml) were pointed out again. Ultrasonography and computed tomography revealed an enlarged tumor (32×15mm) close to the left upper pole of the thyroid. Based upon additional imaging studies, she was provisionally diagnosed with primary hyperparathyroidism. Because serum Ca and iPTH levels were further elevated and the tumor became swollen, a parathyroidectomy was performed. Histopathological examination showed water-clear cell adenoma and no evidence of metastasis. She did well after the operation, and serum Ca and iPTH levels returned to normal values.

Conclusion:Parathyroid water-clear cell adenoma is often seen in 40s to 50s, and serum Ca level does not tend to be so high for increased iPTH level. It is generally believed that resistance to the action of iPTH may exist in this type of parathyroid adenoma; thus, serum Ca may be unlikely to rise to abnormally high level until the tumor get to a certain size. This case also demonstrated a surge of serum Ca level concomitantly with abruptly enlarged parathyroid tumor and extremely higher level of serum iPTH, despite the pre-existence of normocalcemia under the condition of increased iPTH level in 2011. These findings may suggest the possibility of pre-existing parathyroid tumor at the time of the first detection of increased iPTH in 2011, and reflect the feature of parathyroid water-clear cell type adenoma characterized by the resistance to iPTH action, although the details remain unclear.

Nothing to Disclose: MO, MT, TK, YO, AS

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