Delayed Surgery for Parathyroid Adenoma Misdiagnosed as a Thyroid Nodule and Treated with Radiofrequency Ablation
A 53-year-old female presented to our hospital complaining of a 6-month history of backache. Judging from the blood testing results, she had hypercalcemia, and alkaline phosphatase (ALP) was increased to 1,253 U/L (normal range, 35 to 130); the patient was sent to the endocrinology department. Her past history was significant for a surgical procedure for fibrocystoma of her right humerus 20 years ago, and she had donated one of her kidneys to a relative 7 years previously. She had taken atorvastatin 10 mg, amlodipine 5 mg, and omega-3 fatty acid 1,000 mg daily for the past 3 years to treat high blood pressure and dyslipidemia. The patient had been misdiagnosed with a thyroid nodule and hypothyroidism at another hospital 4 years previously and had immediately been prescribed levothyroxine 50 µg/day. At that time, the thyroid ultrasonography revealed two nodules that were 0.3 and 0.5 cm in diameter on her right lobe and another nodule that was 2.3×1.3 cm in size that was projected backwards. She had fine needle aspiration cytology for the nodule on the left lobe, and this had revealed a benign nodule. She had been followed up every 6 months by neck ultrasonography. Two years later, when the nodule on the left lobe of the thyroid had increased in size to 2.9×1.7 cm, they carried out radiofrequency ablation. However, the thyroid nodule remained the same size even after the radiofrequency ablation, so they monitored its size every 6 months for 2 more years (). During that time, the patient began experiencing backache and visited the orthopedics department of our hospital where she was suspected of having metabolic bone disease due to the high serum ALP value.\nThe patient presented with generalized weakness and fatigue without other hypercalcemic symptoms. The peripheral blood examination was as follows: leukocyte count, 7,020/mm3; hemoglobin, 9.3 g/dL; platelet count, 249,000/mm3; prothrombin time (PT), 14.4 seconds (normal range, 11.9 to 14.3); activated partial thromboplastin time (aPTT), 31.3 seconds (normal range, 29.1 to 43.5); serum iron, 65 µg/dL (normal range, 40 to 160); total iron binding capacity (TIBC), 258 µg/dL (normal range, 230 to 430); transferrin saturation, 25%; and ferritin, 158.6 ng/mL (normal range, 13 to 150). Serum chemistry values were also obtained: blood urea nitrogen, 26.9 mg/dL; creatinine, 1.98 mg/dL; glucose, 110 mg/dL; ALP, 1,011 U/L; aspartate aminotransferase, 23 U/L; and alanine aminotransferase, 11 U/L. Serum calcium was 14.6 mg/dL, phosphate was 3.5 mg/dL, and ionized calcium was 7.2 mg/dL. Serum protein and serum albumin were 6.9 and 3.7 g/dL, respectively. The results of the serum electrolyte test revealed that sodium was 135.7 mmol/L, potassium was 4.3 mmol/L, chloride was 104.0 mmol/L, and serum osmotic pressure was 286 mOsm/kg. According to the serum lipid examination, the total cholesterol was 146 mg/dL, triglyceride was 95 mg/dL, high density lipoprotein was 33 mg/dL, and low density lipoprotein was 79 mg/dL. A thyroid function test found T3 was 108.9 ng/dL (normal range, 80 to 200), thyroid stimulating hormone was 0.40 mIU/L (normal range, 0.27 to 4.2), and free T4 was 0.74 ng/dL (normal range, 0.93 to 1.70). Under dual energy X-ray absorptiometry-based bone density examination, the T-score of the lumbar region was -1.4, while the T-scores of the neck were -1.2 on the left and -1.8 on the right. Except for the fifth lumbar vertebra, which had spondylolisthesis, nothing remarkable was found on magnetic resonance imaging.\nAccording to further blood tests, 25-hydroxyvitamin D3 was 9.6 ng/mL (normal range, 4.8 to 52.8), and 1,25-dihydroxyvitamin D3 was 10.5 pg/mL (normal range, 19.6 to 54.3), while the intact parathyroid hormone (iPTH) was 1,911 pg/mL (normal range, 15 to 65). When we performed bone scanning with 99mTc, the amount of cortical bone radioactive isotope uptake increased very high (). Because we suspected hyperparathyroidism, we carried out a 99mTc sestamibi scan and suspected the lesion that had been previously diagnosed as a left thyroid nodule was likely a parathyroid adenoma (). Using thyroid Doppler ultrasonography, we discovered a hypervascular adenoma that was 5-cm-sized solid mass with similar echo of surrounding thyroid tissue in the center, and slightly low echo in outer part in the inferior site of left thyroid gland (), while on the right thyroid parenchyma we discovered two thyroid nodules, 0.3 and 0.5 cm each in diameter, that the patient had had 4 years before. We performed neck computed tomography and found there was no neck lymph node metastastasis and local invasion of other organs ().\nThe patient received both hydration and diuretic treatments until she underwent a surgical operation to control the hypercalcemia; she also had pamidronate 90 mg intravenous injections twice a week. On the 11th day after hydration and diuretic treatment, her condition had improved; serum calcium was reduced to 11.6 mg/dL, and creatinine improved to 1.11 mg/dL. On the 12th day, the patient had left parathyroid excision and was diagnosed with a parathyroid adenoma (). Following the surgical procedure, iPTH normalized to 42.5 pg/mL, but calcium and vitamin D were prescribed for 9 months to cure the hypocalcemia that had developed due to hungry bone syndrome. It has been a year since the surgical operation, and her calcium, phosphate, ALP, and iPTH all remain at normal levels.