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Four-gland exploration remains the gold standard operative approach in the surgical treatment of primary hyperparathyroidism.  Though 85% of patients with primary hyperparathyroidism have a single adenoma causing their illness, the remaining 15% will have double adenomas or hyperplasia.  This latter group requires resection of 2 to 3.5 parathyroid glands to achieve biochemical cure.  Therefore, all parathyroid surgeons must be comfortable with four-gland exploration, and be able to do this safely and efficiently.

The parathyroid glands are some of the most variable parts of the human anatomy.  This can make finding parathyroid glands difficult, especially in light of the fact that normal parathyroid glands are very small (around 40 mg, the size of a grain of rice or a red lentil).  Even though parathyroid surgery is called an “exploration,” this does not mean it is a random search – far from it!  The superior parathyroid glands are very consistent in their location, with 95% lying within 1 cm of the intersection of the inferior thyroid artery and recurrent laryngeal nerve.  Almost all embryologic superior parathyroid glands lie posterolateral to the course of the recurrent laryngeal nerve.  The inferior glands  are more variable in their location, with 65% being applied to the surface of the inferior pole of the thyroid gland.  Most of the remaining inferior parathyroid glands can be found in the thyrothymic tract or the thymus.

The expert parathyroid surgeon has become fluent in not only the common locations of the parathyroid glands, but also draws upon a vast experience of unusually located glands.  Walking this path requires thousands of cases.  The seemingly infinite variability of individual parathyroid anatomy ensures that parathyroid surgery will always be challenging and humbling, even for the most experienced surgeons.