SAT230 A Case Of Pseudohypoparathyroidism Without Any Hereditary Features

Disclosure: I. Haque: None. L.A. Robles: None. Background: Pseudohypoparathyroidism (PHP) refers to a heterogeneous group of disorders characterized by resistance to parathyroid hormone. PHP type Ib is characterized clinically by isolated renal PTH resistance manifesting as hypocalcemia, hyperphosphatemia, and increased serum PTH. About 60-70% of patients also present with elevated TSH levels due to TSH resistance. We present a unique case of adult onset PHP. Clinical Case: A 30-year-old woman admitted to the hospital for recent onset recurrent hypocalcemia with symptoms of weakness, muscle spasm and cramps. Until recently she was in a normal state of health. Admission labs revealed ionized calcium 0.78 (1.15 - 1.30 MM/L) , serum Ca 6.2 (Albumin 4.3). PTH elevated to 364. Creatinine 0.54 mg/dl, GFR 131 ml/min. Vit D level 35, Bone ALP 49.3 (premenopausal female :4.5-16.9 UG/L), Mag 1.9 , Ph 6.6. A 24-hour urine collection for Ca showed a value of 14 mg/24hr (50 - 400 MG/24H). Additionally, she was found to have a TSH <0.01 and Free T4 1.1. These labs confirmed PTH-resistant hypocalcemia and hyperphosphatemia with concurrent hyperthyroidism. Thyroid Ultrasound demonstrated a possible parathyroid adenoma on the left measuring 0.8x0.4x0.7 cm, which we suspect was a result of hyperplasia from PTH hypersecretion secondary to PTH resistance. TSI and TRAB antibodies were later found to be positive confirming grave’s hyperthyroidism. She had a similar presentation about 3 months earlier with symptomatic hypocalcemia and was discharged on Calcitriol, Ca CO3, and Cholecalciferol. Prior to this including through childhood, patient denies symptoms or lab abnormalities. Patients’ physical exam shows a height of 5ft 4-inch, weight 78kg, BMI 29.7. She had no abnormal facial features or skeletal/digit abnormalities. Patient reached all physical and cognitive milestones at expected times through childhood. Her calcium supplementation was adjusted to calcium carbonate 2000 mg every 8 hours, calcitriol 1 mcg twice daily, cholecalciferol 1000 units daily. Her total calcium improved to 7.4, ionized calcium improved to 0.93, phosphorus remained elevated at 6.1. Patient was discharged at her will due to personal social commitment. She was also started on Methimazole 5mg daily on discharge. Follow up labs showed Ca remained stable and eventually normalized on the above Ca supplementation 6 months after discharge. Conclusion: Unlike PHP Ia, patients with PHP Ib usually lack the physical characteristics of Albright hereditary osteodystrophy (round facies, short stature, short metacarpal bones (especially III-V), obesity, subcutaneous calcifications, and developmental delay), and typically show no other endocrine abnormalities, although our patient presented with subclinical hyperthyroidism. Typically, PTH-resistance disorders present as symptomatic hypocalcemia in childhood, however our patient presented in adulthood. Presentation: Saturday, June 17, 2023