山本 浩之¹, 貴田岡 正史¹, 森田 恒治², 相田 真介³, 清水 誠一郎³

Hiroyuki YAMAMOTO¹, Masafumi KITAOKA¹, Kouji MORITA², Shinsuke AIDA³, Seiichirou SHIMIZU³

¹公立昭和病院内分泌・代謝内科, ²公立昭和病院乳腺・内分泌外科, ³公立昭和病院病理診断科

¹Division of Endocrinology and Metabolism, Showa General Hospital, ²Division of Breast and Endocrine Surgery, Showa General Hospital, ³Division of Diagnostic Pathology, Showa General Hospital

キーワード : hyperparathyroidism, three-dimensional ultrasonography, coronal section image, MIBI scintigraphy

症例は72歳，女性．尿路結石および胸椎圧迫骨折の既往があり，骨粗鬆症・Ca高値・P低値・iPTH高値の所見から原発性副甲状腺機能亢進症の疑いで当院紹介となった．Bモード断層像で甲状腺左葉前面に接する扁平な低エコー領域が存在し，power Doppler法で同部位に血流を認めた．3次元超音波法では冠状断面で長径16 mmの楕円形の低エコー領域として描出された．MIBIシンチグラフィーでは早期像で甲状腺に正常な集積があり，後期像で甲状腺左葉下部に結節状の集積残存がみられ，冠状断面像と形態が一致していた．他に異所性副甲状腺は認めず，手術により摘出し術後病理で副甲状腺であることが確認された．下副甲状腺は発生学的に頚部から縦隔にかけて広範囲に存在し得ることが知られているが，甲状腺前面に認めることはまれであり，病変の同定に3次元超音波法が有用であった．

A 72-year-old woman with a history of urolithiasis and thoracic compression fracture was referred to our hospital for evaluation of primary hyperparathyroidism. She had osteoporosis, hypercalcemia, hypophosphatemia, and elevated intact PTH. B-mode ultrasound revealed a flat hypoechoic area adjacent to the anterior surface of the thyroid, and power Doppler imaging revealed blood flow in the same area. Three-dimensional ultrasonography revealed an oval hypoechoic area in a coronal section image, measuring 16 mm in the major axis. MIBI scintigraphy showed normal uptake in the thyroid in the acute phase, and nodular remaining uptake in the left lower pole of the thyroid in the delayed phase, whose shape was quite similar to that of the coronal section image. No other ectopic parathyroid gland was found. This hypoechoic area was revealed to be an enlarged parathyroid gland, which was confirmed by postoperative pathology. Although it is well known that the lower parathyroid gland can be found anywhere from the cervical region to the mediastinum due to its embryological procedure, a parathyroid gland on the anterior surface of the thyroid is rarely documented. Three-dimensional ultrasonography was useful for identifying the lesion.