methimazole and Hypoparathyroidism

A 29-year-old pregnant woman with Graves' disease presented with severe persistent hypocalcaemia after thyroidectomy. Six months prior to presentation she was diagnosed with Graves' disease and remained uncontrolled with methimazole. She was confirmed pregnant prior to radioactive iodine ablation (RAI), and underwent total thyroidectomy during her second trimester. After surgery, continuous intravenous calcium infusion was required until delivery of the fetus allowed discontinuation at postoperative day 18, despite oral calcium and calcitriol administration. A total of 38 g of oral and 7.5 g of intravenous elemental calcium was administered. We report an unusual case of recalcitrant hypocalcaemia thought to be due to a combination of postoperative hypoparathyroidism, combined with thyrotoxic osteodystrophy and pregnancy, after surgical correction of Graves' disease. Increased vigilance and early calcium supplementation should be a priority in the management of these patients.

Topics: Administration, Oral; Adult; Antithyroid Agents; Calcium; Drug Administration Schedule; Female; Graves Disease; Humans; Hypocalcemia; Hypoparathyroidism; Infusions, Intravenous; Methimazole; Pregnancy; Pregnancy Complications; Pregnancy Trimester, Second; Thyroidectomy; Thyrotoxicosis; Time Factors; Treatment Outcome

A 57 year old female came with the complaint of recurrent headache, often fatigue, and sometimes feel numbs and rigid in her extremities, no other symptom was noted. Her body weight is stable and she was in menopausal state. She had a history of partial thyroidectomy 20 years ago and continues thiamazole 2.5 mg with seldom regular consult to physician. From the physical examination, the patient had a scar from thyroid surgery and other organs were in the normal condition. From laboratory examination, there was slight normocytic normochromic anemia (Hb: 10.7 gr/dL), normal fT4: 1.21 ng/dL (0.7-1.48 ng/dL), slightly low Calcium: 8.3 mg/dL (8.5-10.2 mg/dL), others were within normal limit but there was no Phosphorus level data. She was currently on medication: thiamazole 2.5 mg once daily, CaCO3 500 mg once daily, and alfacalcidol 1 mcg once daily, to prevent the rigid and numbness that she felt before. For further investigation, we performed a PTH test with result of hypoparathyroidism with parathyroid hormone 7 pg/mL (15-65 pg/mL) and brain CT-scan with result there was a symmetrical bilateral calcification in radiate corona, frontal lobes, temporal lobes, basal ganglia, thalamic, and dentate nuclei of cerebelli. There was no data about the histopathology examination of the thyroid tumor because the patient did not keep the data. The mechanism of intracranial calcification in hypoparathyroidism, more often seen in pseudohypoparathyroidism than in idiopathic hypoparathyroidism, has not been completely elucidated. It may be related more to the duration of hypocalcaemia and hyperphosphataemia than parathyroid hormone itself. Hyperphosphataemia promotes ectopic calcification in brain tissue in hypoparathyroidism. Intracranial calcification is one of the features of chronic hypocalcemia, and the calcifications typically involve basal ganglia, thalami, and the cerebellum.

Topics: Brain; Calcinosis; Calcium; Female; Humans; Hypocalcemia; Hypoparathyroidism; Methimazole; Middle Aged; Thyroidectomy; Tomography, X-Ray Computed