Parathyroid gland anatomical distribution and relation to anthropometric and demographic parameters: a cadaveric study.

Parathyroid glands play an important role in controlling calcium levels, which influence muscular contraction and neurotransmission. The number of variants, localization and ectopic positions make these glands tricky during surgical exploration. Detailed anatomical knowledge of these glands is fundamental to avoid postsurgical hypoparathyroidism, such as failures during thyroidectomy and parathyroid procedures. The purposes of this work were to study and report practical knowledge for surgeons in order to localize the glands. Dissections were performed on 56 cadavers. Gland identity was confirmed by histological study. Also, mediastinal tissue and the carotid sheath were treated with Carnoy's solution to identify ectopic glands. The thyroid gland was divided and sliced to identify parathyroid glands in the parenchymal and subcapsular space. Four or more parathyroid glands were found in 89.3% of the studied specimens. Mean gland weight was 33.1 mg, and its mean measurements were 6.7 × 3.9 × 2.0 mm. In more than 90% of the cases there was a correlation with the inferior laryngeal nerve and the parathyroid glands: the upper glands were located in medial positions, and the lower ones were found to be located laterally. In 42.8% of cases at least one ectopic gland was observed. The main ectopic regions were the mediastinum and thymus (19.6%), thyroid subcapsular space (12.5%) and thyroid parenchyma (5.4%). Quantity, gland characteristics and location were not influenced by anthropometric and demographic parameters. Here we show the high incidence of parathyroid glands positioned at "abnormal" locations, and as a controversial topic in endocrine surgery, this matter must be continuously studied and reported in the literature.