7320 A Case Of Concurrent Lithium-Associated Hyperthyroidism, Nephrogenic Diabetes Insipidus, Primary Hyperparathyroidism, And Acute Pancreatitis

Abstract Disclosure: C. Buchanan: None. C. Ellenburg: None. M. Beasey: None. Background: Hyperthyroidism, nephrogenic diabetes insipidus, and hyperparathyroidism are all well-documented adverse effects of long-term lithium therapy. This report highlights a rare case of these three endocrinologic adverse effects occurring concurrently. Clinical Case: A 47-year-old man on long-term lithium therapy for bipolar disorder presented with slurred speech, fatigue, new tremor, and generalized muscle weakness. Laboratory testing was consistent with lithium toxicity with serum lithium level of 2.22 mmol/L (0.60-1.50). Thyrotoxicosis was present with a free T4 of 3.2 ng/dL (0.6-1.1) and TSH of 0.04 µlU/mL (0.24-5.60). CT of the neck revealed mild enlargement and heterogeneity of the left lobe of the thyroid gland. Methimazole was started. Calcium corrected for albumin was elevated at 12.4 mg/dL (8.6-10.0) and PTH was also elevated at 146.0 pg/mL (12.0-88.0). Serum sodium was elevated at 160 mmol/L (136-145) with urine osmolality of 327 mOsm/kg. DDAVP was trialed in addition to IV hypotonic fluids, although it had little effect. Acetazolamide was started a few days later with subsequent normalization of the serum sodium level. Acetazolamide was later discontinued in favor of hydrochlorothiazide because of the development of non-anion-gap metabolic acidosis. A dose of zoledronic acid was given and cinacalcet was started. Serum calcium normalized over the following week. The patient acutely developed right upper quadrant abdominal pain, nausea, and emesis on hospital day 13. Lipase was elevated at 575 u/L (11-82). CT of the abdomen demonstrated moderate inflammatory changes along the pancreas and duodenum. Acute pancreatitis was diagnosed. There were no gallstones or acute biliary tract abnormalities seen on ultrasound. The patient’s symptoms gradually improved and he was discharged from the hospital after a total of 18 days. Lithium was discontinued indefinitely. TSH and free T4 normalized within 3 months. He had continued to require hydrochlorothiazide, methimazole, and cinacalcet at the time of his 3-month primary care follow-up appointment. Conclusion: Despite its efficacy and widespread use in mood stabilization, lithium has a narrow therapeutic window and is strongly associated with several serious, sometimes irreversible, adverse effects. Routine monitoring of lithium levels, serum calcium, and thyroid hormone levels is required. Lapses in routine monitoring may, as in this case, result in significant morbidity and prolonged hospitalization. Presentation: 6/1/2024