Contents ：
ü Patients with suspected primary hyperparathyroidism (1°HPTH) are frequently referred to endocrinologists to confirm a diagnosis and recommend treatment.
ü Once a diagnosis of 1°HPTH is confirmed, imaging studies are often obtained both to assist in determining disease etiology and to direct operative planning.
ü Early efforts at parathyroid localization were of limited utility.
ü The superior glands are derived from the fourth branchial pouch and are less variable in location owing to their shorter descent during embryological development.
n 80% located posterior to the midportion of the thyroid at the level of the cricoid cartilage.
ü The inferior glands, derived from the third branchial pouch along with the thymus.
n Typically located posterior to the inferior pole of the thyroid.
n More inconsistent in location due to their lengthier migration.
ü Ectopic superior glands are most commonly found within the thyroid gland or capsule(parafollicular cells of the thyroid are also derived from the fourth branchial pouch).
ü Ectopic inferior glands can be located anywhere along their shared descent with the thymus from the third pouch.
n Thyrothymic ligament or within the thymus.
n Less common : neck or carotid sheath, retroesophageal locations, and within the mediastinum.
ü The principle of sestamibi parathyroid scanning is that
n MIBI tracer is taken up by both the thyroid and parathyroid adenoma.
n Washes out of the thyroid faster than the parathyroid.
n Early images at 20 minutes after injection are obtained, followed by delayed images typically at 2 hours.
ü Recently, a new CT-based parathyroid imaging modality termed 4-dimensional (4D)-CT has emerged, with the extra dimension referencing time.
ü Overall 4D-CT sensitivity is approximately 90% and can correctly localize the quadrant of a single adenoma in 85% of cases.
ü Parathyroidectomy
n The principles of 4-gland exploration, which is essential for treatment of hyperplasia, 2 o HPT, and tertiary hyperparathyroidism.
n With the ability to preopeatively localize an adenoma with imaging - unilateral exploration became acceptable.
n Limitation : a second adenoma {double adenoma) on the contralateral side can be missed.
n Radioguided parathyroidectomy, in which technetium sestamibi is injected prior to surgery and a gamma probe is then used to compare the radioactive level before and after excision adenoma.
Discussion ：
Dr.Houng ： ntraoperative PTH can be used as an adjunct in focused explorations to assure biochemical success.
Conclusion ：
Dr.Ho ： MIRP, not only reduces the cost to both the hospital and the patient, but importantly, also decreases the time under anesthesia.
