Endocrine Abstracts

Ectopic parathyroid glands arise from aberrant migration during early stage of development. Lack of successful identification leads to failed parathyroid surgery and persistent hyperparathyroidism.

Case History: A 57-year-old lady presented with abdominal discomfort and diffuse bone pain. Her corrected serum calcium was raised at 2.81mmol/l, reduced serum phosphate with an inappropriate intact PTH concentration of 10.5 pmol/l. Initial, vitamin D level was low at 16 nmol/l and after treatment, levels rose to 40 nmol/l with persistent hypercalcaemia and elevated PTH. Neck ultrasound and 4DCT Parathyroid were consistent with a right inferior parathyroid adenoma.

Treatment: She underwent neck exploration which proved difficult. All four parathyroid glands appeared normal. An additional gland was found on the right inferiorly in the thyrothymic ligament, which was removed. Histology revealed partially regressed thymus tissue and ectopic parathyroid tissue. Following surgery, she developed palpitations and anxiety, and was hyperthyroid with raised free T4 and free T3 with suppressed TSH. She was offered symptomatic treatment with propranolol as needed. Her thyroid function normalised 4 weeks after surgery. Her corrected calcium rapidly returned to normal and the PTH level was recorded at 1.9 pmol/l. She is currently well, not requiring calcium supplements.

Conclusion: Parathyroidectomy has a success rate of >95 % for cure. In about 6-16 % of cases, hyperfunctioning parathyroid gland(s) are found in an ectopic location. Ectopic parathyroid are most frequently found in the anterior mediastinum, the thymus, or the thyroid gland. In our case, ectopic parathyroid tissue seen in the thymus which shares an origin with the parathyroid glands during development. Manipulation of the thyroid at surgery causes transient hyperthyroidism. Intraoperative handling impairs the physical integrity of the cells, with consequent inflammatory response and histologically results in a multifocal granulomatous folliculitis. Usually causes self-limiting hyperthyroidism and clinically significant thyrotoxicosis occurs in a minority. Awareness of this disorder is important to avoid inappropriate treatment.