Endocrine Abstracts

Section 1: Case history: A 30 year-old female patient with a background of symptomatic primary hyperparathyroidism diagnosed in 2008 and a history of two failed neck surgeries, was reviewed in clinic complaining of persistent symptoms of hypercalcaemia. Previous pre-operative neck imaging had failed to localise a parathyroid adenoma and the patient had undergone two neck explorations by an experienced ENT surgeon; one which removed thymic tissue and the other which removed a mildly hyperplastic right inferior parathyroid gland. The patient’s mother had been diagnosed with PHPT, but genetic studies for hyperparathyroidism were all negative.

Section 2: Investigations: Biochemistry revealed elevated serum calcium of 3.05 mmol/l, and an elevated PTH of 18.02 pmol/l. 24 h urinary calcium was also elevated at 17.34 mmol/24 h. Additional localisation was arranged including an ultrasound of the neck, which did not identify an abnormal parathyroid but demonstrated a solitary left lower pole thyroid nodule. A subsequent 4D CT scan again showed a left thyroid nodule measuring 12×8 cm which demonstrated avid contrast enhancement and washout most in keeping with a parathyroid adenoma. No other abnormal parathyroid was identified. A Methionine PET-CT showed a focus of high tracer uptake in the same left-sided intra-thyroidal nodule.

Section 3: Results and treatment: As this patient had two previous failed neck surgeries, we were keen to ensure that the future surgery would be curative. An US-guided fine needle aspiration of the left sided intrathyroidal nodule was performed and samples reserved for cytology and parathyroid hormone measurement. Immunohistochemistry was positive for chromogranin A but negative for TTF-1, in keeping with parathyroid rather than thyroid tissue, and cytological appearances favoured parathyroid tissue. PTH measurement from the FNA sample was 726 pmol/l (levels > 10 pmol/l consistent with sampling from parathyroid tissue). The patient subsequently underwent a left hemi-thyroidectomy and pathology confirmed a left thyroid lobe containing an enlarged, well circumscribed, intrathyroidal parathyroid gland. Post-operatively serum PTH and calcium levels normalised.

Section 4: Conclusions and points for discussion: In this case, we present a patient who had refractory PHPT despite two previous neck operations. An intrathyroidal parathyroid adenoma was subsequently detected on 4D CT and Methionine PET CT and confirmed by a fine needle biopsy. In this case, the PTH level in the aspirate and the ratio between aspirate PTH and serum PTH (59 times) confirmed the suspicion of an intrathyroidal parathyroid adenoma. This case highlights the potential utility of fine needle aspiration in selected cases to confirm a diagnosis of a parathyroid adenoma.