SUN-495 Resolution of Hypocalcemia during Pregnancy in Chronic Hypoparathyroidism

Background : Hypoparathyroidism is one of complication after thyroid, parathyroid, or radical neck dissection for head and neck cancer, which may be transient or permanent; or even intermittent. It can improve with improvement in PTH level gradually, otherwise continuous calcium and calcitriol supplementation is warranted to maintain calcium level. We present an interesting case of non PTH mediated post-surgical hypothyroidism resolution during pregnancy. Clinical Case: 22-year-old female presented to PCP with mass in her neck. Thyroid US revealed 3.3 cm left lobe nodule. Subsequent FNA of nodule showed Papillary thyroid carcinoma (PTC) and underwent total thyroidectomy with central and level 2-5 neck dissection. Pathology confirmed metastatic PTC (multifocal, sclerosing variant, largest 2.1 cm) with vascular invasion, 20/53 LN + with largest LN 0.8 x 0.5 cm. Post operatively she developed hypocalcemia with nadir corrected calcium (Cca) level of 7.2 mg/dl few days after surgery with undetectable PTH level. She had symptomatic hypocalcemia and needed high dose calcium and calcitriol replacement during hospitalization. She was discharged with elemental calcium 1000 mg TID, Vitamin D 200 IU TID, calcitriol 0.5 mcg daily and ergocalciferol 50000 units per week. She was supposed to receive radioactive iodine treatment after surgery, but it was held as she became pregnant. She was started on Levothyroxine. During follow up visit in 12 weeks of her gestation, she reported that she had stopped taking all her medications except levothyroxine for 1 month and reports no symptoms of hypocalcemia. Labs result showed Cca of 8.3 mg/dl, PTH again undetectable range, PTHrp 13 pg/ml (14 -27). she was advised to restart her medications and repeat Cca was 9.5 mg/dl, 25-OH Vitamin D 39.6 ng/ml and 1,25dihydroxy Vitamin D is 78.8 pg/ml (20-82), urine calcium-creatinine ratio 309 mg/gm. we stopped Calcitriol, ergocalciferol and continued with calcium/Vitamin D tablets. After stopping calcium, again calcitriol level was 78.6 pg/ml. she remained asymptomatic. Conclusion: Our case with post-surgical Hypoparathyroidism which resolved during pregnancy without improvement in PTH level is very rare and interesting. Literature review suggests that the placenta during pregnancy and breast tissues during lactation may produce PTHrP. But PTHrP in our case is low which excluding it as possible mechanism. There can be increased activity of 1 alpha hydroxylase by prolactin, estradiol and placental lactogen hormone which can increase calcitriol. It is in high normal level in our cases suggesting possible causes of resolution of hypocalcemia. We still need to monitor her for change in calcium level during her entire pregnancy which can affects her outcome. This case indicates we need to be vigilant and monitor calcium level closely during pregnancy.