Bilateral giant parathyroid adenoma in the absence of multiple endocrine neoplasia type 1

Abstract

Introduction

Bilateral giant parathyroid adenoma in the absence of multiple endocrine neoplasia (MEN) type 1 is extremely rare and literature on this subject is limited.

Case history

A 79-year-old man presented with acute kidney injury secondary to hypercalcaemia. Blood test results indicated primary hyperparathyroidism. Ultrasonography revealed bilateral parathyroid adenomas measuring 19.4mm x 19.5mm x 18.8mm (left) and 15.2mm x 18.3mm x 19.6mm (left) whereas on computed tomography, the measurements were 31mm x 20mm (left) and 30mm x 14mm (right). Intraoperatively, giant adenomas measuring 50mm x 25mm x 12mm (left, weighing 8.101g) and 48mm x 22mm x 10mm (right, weighing 7.339g) were identified and excised. Parathyroid hormone level dropped from 44.6pmol/l preoperatively to 8.9pmol/l postoperatively (normal range 1.3–7.6pmol/l). The patient was discharged with no complications.

Conclusions

We report a rare phenomenon where bilateral giant parathyroid adenoma occurred in the absence of MEN type 1. It highlights the importance of cross-sectional imaging in delineating the anatomy of adenomas as their size can be grossly underestimated by ultrasonography alone.

Introduction

Primary hyperparathyroidism is characterised by inappropriate secretion of parathyroid hormone (PTH), leading to high serum calcium concentration. This usually results from the enlargement of a single parathyroid gland or parathyroid adenoma. Giant parathyroid adenomas are defined as those larger than 3g. Bilateral giant adenomas in the absence of multiple endocrine neoplasia (MEN) type 1 are extremely rare. We report a patient with bilateral giant parathyroid adenomas, in the absence of MEN, presenting with severe hypercalcaemia and successfully treated with surgical excision of the adenomas. Initial imaging with ultrasonography and computed tomography (CT) underestimated the actual size of the adenomas.

Case history

A 79-year-old man was initially admitted with right obstructive nephropathy and acute kidney injury secondary to hypercalcaemia. In the same admission, he was noted to have an adjusted calcium level of 3.29mmol/l (normal range 2.12–2.62mmol/l) and a PTH of 44.6pmol/l (normal range 1.3–7.6pmol/l). Selected blood test results are shown in Figure 1. His background medical history was limited to chronic obstructive pulmonary disease.

Figure 1.

Selected blood test results

The patient was reviewed by endocrinologist as well as ear nose and throat surgeons. He was investigated with ultrasonography of the neck, which confirmed bilateral parathyroid adenomas, measuring 19.4mm x 19.5mm x 18.8mm on the left and 15.2mm x 18.3mm x 19.6mm on the right (Fig 2). He went on to have technetium-99m sestamibi imaging to localise the parathyroid adenoma (Fig 3). CT of the neck and chest was also carried out. This showed the adenomas to be larger than reported by ultrasonography, measuring 31mm x 20mm on the left and 30mm x 14mm on the right with central necrosis seen within these lesions (Fig 4). MEN type 1 was excluded as full-body CT did not reveal the presence of any other tumours and he had no clinical or biochemical signs of other endocrine tumours.

Figure 2.

Ultrasonography of left (A) and right (B) parathyroid adenomas

Figure 3.

Sestamibi imaging showing bilateral parathyroid adenomas (asterisks)

Figure 4.

Axial (A) and coronal (B) computed tomography showing bilateral giant parathyroid adenomas (asterisks)

In terms of management, the patient was started on cinacalcet 30mg three times a day but was unfortunately not able to tolerate it as it gave him delusions. Following endocrine multidisciplinary team (MDT) discussion, he was diagnosed with primary hyperparathyroidism and was fast tracked for parathyroidectomy in view of the presence of kidney stones. The endocrine MDT could also not find any clinical, biochemical or radiological evidence of MEN type 1. During surgery, bilateral giant parathyroid adenomas were seen (Fig 5). Following excision of the left parathyroid adenoma, intraoperative PTH dropped from 39.1pmol/l to 26.6pmol/l. This reduced further to 8.9pmol/l following removal of the right parathyroid adenoma. Both specimens were sent for histology evaluation. The patient had a planned admission to the high dependency unit after surgery due to comorbidity. He recovered well and was discharged from hospital the following day after drain removal when output was less than 30ml.

Figure 5.

Intraoperative photographs of left (A) and right (B) parathyroid adenomas

Postoperative histology showed the left parathyroid adenoma to be 50mm x 25mm x 12mm (weighing 8.101g) and the right parathyroid adenoma to be 48mm x 22mm x 10mm (weighing 7.339g). This was larger than findings from both ultrasonography and CT. Microscopic examination revealed no evidence of malignancy. Three months after the operation, the patient’s adjusted calcium was 2.36mmol/l, PTH was 3.6pmol/l and vitamin D was 70nmol/l.

Discussion

Bilateral giant parathyroid adenoma is a rare phenomenon in the absence of MEN type 1. We conducted a search of the Embase and PubMed databases (from 1946 to 2019 week 18) using the keywords “parathyroid adenoma”, “giant” and “bilateral” and used the same search terms on Google. This revealed only three case reports of bilateral giant parathyroid adenoma.^1–3 The largest of these weighed 102g (left) and 74g (right).¹ In comparison, normal parathyroid glands weigh 30–50mg.⁴ One of the case reports described an ectopic giant parathyroid adenoma alongside bilateral parathyroid adenomas.³ None of the patients reported had bilateral adenomas in the absence of MEN type 1.

Accuracy of preoperative imaging is important as it is helpful for surgical planning and avoidance of unplanned conversion to extended bilateral neck exploration. In our case, ultrasonography was less accurate than CT for the estimation of adenoma size. This is consistent with findings from other studies reporting significantly higher positive predictive value and sensitivity of single photon emission computed tomography – computed tomography (SPECT-CT) (93.0% and 80.3% respectively) compared with ultrasonography (78.3% and 63.2% respectively) in preoperative localisation of parathyroid adenomas.⁵

Superiority of CT over ultrasonography could be due to the fact that it allows for delineation of the anatomy of the entire adenoma whereas only part of the adenoma is visualised transcervically on ultrasonography. In addition, ultrasonography is highly dependent on the experience of the sonographer in performing and interpreting the study, and its findings can be limited by body habits and gland morphology.⁶ Recent introduction of four-dimensional CT utilises both arterial and venous phases, and has been shown to have superior preoperative localisation of adenoma compared with sestamibi SPECT-CT in patients with both single and multigland disease.⁷ This technique is now increasingly used in patients with recurrent or persistent primary hyperparathyroidism.

Conclusions

We report a case of bilateral giant parathyroid adenomas, weighing 7.339g and 8.101g, in the absence of MEN type 1. The patient presented with severe hypercalcaemia and was successfully treated with surgical excision of the adenomas. Initial imaging with both ultrasonography and CT underestimated the size of the adenomas although CT results were closer estimates of the actual size.