Surgical treatment of primary hyperparathyroidism is successful in more than 95% cases but coincidence of ectopic parathyroid gland position and inconclusive or false positive localisation studies can be challenging even for experienced endocrine surgeons.

The case study of the patient with sporadic primary hyperparathyroidism in whom first operation was unsuccessful due to abnormal position of the adenoma of supernumerary parathyroid gland „hidden" at the base of the skull and false positive scintigraphy.

Patient was diagnosed with primary hyperparathyroidism. During the first operation we found normal 4 parathyroid glands in normal positions while in the place of 99mTc-MIBI uptake there was only brown adipose tissue which was excised. Histopathological examination of the biopted parathyroids was inconclusive. The postoperative scintigraphy did not revealed MIBI accumulation anymore. The patient underwent second operation - subtotal parathyroidectomy resulted in the insignificant PTH drop so we've came to conclusion that beyond 4 normal glands there was an ectopic parathyroid adenoma and we've decided to autotransplantate resected glands. Contrast enhanced CT revealed adenoma of undescended supernumerary parathyroid at the base of the skull. After the excision of this nodule we observed significant intraoperative drop of PTH from 158 pg/ml to 22,4 pg/ml. In the postoperative period patient had normal PTH levels and transient hypocalcemia.

Surgical parathyroid treatment is often simple but could be challenging in some cases. It is important to remember about embryology and anatomy of the parathyroid glands that gives us information about number and localization, which is not constant.