NDT Advance Access originally published online on August 25, 2006
Nephrology Dialysis Transplantation 2007 22(1):293-295; doi:10.1093/ndt/gfl503
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Intrathyroidal supernumerary parathyroid gland in hyperparathyroidism after renal transplantation
Email: fabiomonte{at}uol.com.brSir,
Supernumerary parathyroid glands are more frequently described in secondary hyperparathyroidism (HPT) than in primary HPT cases. The presence of a supernumerary intrathyroidal gland is rare, but has important surgical implications. A 52-year-old female with membranous glomerulonephritis started haemodialysis in 1990. After 72 months she underwent a cadaveric renal transplantation. Three years after renal transplantation, her calcium level reached 12.7 mg/dl and parathyroid hormone (PTH) was 486 pg/ml (10–65 pg/ml). She had a normal serum creatinine. A pre-operative 99m-technetium sestamibi (MIBI) scan was consistent with parathyroid hyperplasia, and a high uptake in the parathyroid at the left side was suggested (Figure 1). Surgical exploration showed four topic parathyroid glands. The left superior pole of the thyroid was long and high in the neck. Inside this pole a small nodule was palpable. Four topic parathyroid glands and the left thyroid lobe were excised (Figure 2). Cut surface of the thyroid was suggestive of a supernumerary intrathyroidal hyperplastic parathyroid gland, which was confirmed by histology.
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The detection of an intrathyroidal parathyroid gland is expected to be four times more common in hyperplasia than in uniglandular disease [1]. Proye et al. [2] have found intrathyroidal parathyroid glands in 2.3, 3.8 and 10.0% of the patients with adenoma, primary hyperplasia and renal HPT patients, respectively.
Some authors advise blind thyroidectomy when one gland is missing after careful evaluation of other neck sites, detecting the missing gland inside the thyroid in almost 60% of the cases [2]. Other authors have a different opinion, with a yield of 17% of intrathyroidal parathyroid after blind lobectomy [3]. Blind thyroidectomy may pose difficulties for further surgical exploration, with an increased risk of laryngeal nerve damage.
Pre-operative ultrasonography may be useful to evaluate an associated thyroid disease and has a sensitivity of 95% in disclosing intrathyroidal parathyroid [3]. If available, intra-operative ultrasonography may spare normal thyroid tissue, thus avoiding blind thyroid lobectomy.
Even though MIBI scan has limitations in revealing all hyperfunctioning parathyroid tissue, it may reveal ectopic glands and in this specific case, an intrathyroidal parathyroid. Considering the effectiveness and low morbidity of this method, the routine use of MIBI scan and pre-operative ultrasonography may be combined to increase the success rate of parathyroid operations related to renal HPT, as these patients have a variable but recognized increased risk for surgical management.
Supernumerary intrathyroidal parathyroid glands are rare, occurring in 0.1% [4] to 0.25% [2] of cases and in 1.1% of reoperations for HPT [3]. Although rare, supernumerary intrathyroidal parathyroid glands should be remembered as a cause of persistent or recurrent secondary HPT, and these glands may in part explain the persistence of elevated PTH levels after an ‘extended exploration’ that includes bilateral thymectomy and central neck dissection [5].
Conflict of interest statement. None declared.
1Department of Head and Neck Surgery
2Transplant Renal Unit
3Department Radiology and Nuclear Medicine the Hospital das Clinicas
University of Sao Paulo
Medical School
Sao Paulo
Brazil
References
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- Russel CF, Grant CS, VanHeerden JA. (1982) Hyperfunctioning supernumerary parathyroid glands. Mayo Clin Proc 57:121–124.[Web of Science][Medline]
- Kaczirek K, Prager G, Riss P, et al. (2006) Novel parathyroid hormone (1–84) assay as basis for parathyroid hormone monitoring in renal hyperparathyroidism. Arch Surg 141:129–134.
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