Endocrine Abstracts

Aim: Although nonsecretory parathyroid carcinoma is relatively more frequent, nonsecretory parathyroid adenoma was also reported. It is thought to precede functioning parathyroid adenoma.

Case report: An iso-hypoechoic 6.5×9.5×16.1 mm thyroid nodule with irregular borders in the superior-posterior part of right thyroid lobe was observed in ultrasonography in a 44-year-old female euthyroid patient. Fine-needle aspiration (FNAB) biopsy resulted with non-diagnostic cytology (degeneration of follicular epithelial cells, colloidal material). A second FNAB was recommended but she admitted five years later. There was subclinical hypothyroidism with positive thyroid auto-antibodies and normocalcemia in laboratory examination. The nodule in the superior-posterior part of right thyroid lobe was well circumscribed and hypoechoic with diameters of 5.4×13.2×18.1 mm. The ultrasonographical apperarence was found to be suspicous for an intrathyroidal parathyroid adenoma. Serum calcium was 8.99 mg/dL, albumin was 4.6 g/dL, parathyroid hormone was 70.22 pg/mL and 25-OH Vitamin D3 was: 6.52 ng/mL. Parathyroid hormone decreased to 37.94 pg/mL after replacement of vitamin D. The lesion was evaluated with FNAB and the cytological result was again nondiagnostic (small amount of colloidal material, a few epithelial cells). Parathyroid hormone washout was >5000 pg/mL in fine-needle aspiration fluid. 24-hours urinary calcium excretion was 210 mg. In Tc99m-sestamibi SPECT/CT revealed persistent activity at superior-posterior part of upper pole of the right thyroid lobe. There was increased echogenity compatible with crystalloid in urinary system ultrasonography. Z score was within the expected range for age in bone mineral density. Surgical excision of the lesion was performed and a parathyroid adenoma was confirmed histopathologically.

Conclusion: Parathyroid hormone washout should be considered in a lesion with suspicion of intrathyroidal parathyroid adenoma even when primary hyperparathyroidism can not be shown biochemically. If surgery is not performed, patients should be followed for possible development of primary hyperparathyroidism.