Pomalidomide

Abstract

Hyponatraemia due to hypothyroidism: case report A 70-year-old man developed hypothyroidism complicated by hyponatraemia, during treatment with pomalidomide for relapsed and refractory multiple myeloma (RRMM). The man was diagnosed with stage II IgG kappa multiple myeloma (MM) in April 2016. He underwent plasmapheresis and received treatment with bortezomib, dexamethasone and lenalidomide. In November 2017, he underwent autologous stem cell transplant and was maintained on lenalidomide. In January 2019, he was diagnosed with RRMM. Therefore, he started receiving treatment with pomalidomide [route and dosage not stated], daratumumab and dexamethasone. However, during eighth cycle of the chemotherapy, he presented with decreased appetite for 2 weeks, and fatigue. His lab tests revealed the following: sodium levels of 120 mEq/L, creatinine of 1.1 mg/dL, glucose of 172 mg/dL, WBC 2.49 × 103/μL, Hb 102 g/L, platelets 72 × 109/L, total neutrophils 1.2 × 103/μL, total protein 8.7 g/dL, albumin 4 g/dL and globulin 4.7 g/dL. He was diagnosed with hyponatraemia. The man was admitted for severe hyponatraemia with sodium levels of 116 mEq/L and received treatment with sodium chloride [normal saline]. After admission, his lab tests showed: glucose 129 mg/dL, creatinine 1.2 mg/dL, protein 7.8 g/dL, albumin 3.6 g/dL and globulin 4.2 g/dL. Hyponatraemia workup revealed plasma osmolarity of 256 mOsm/kg, urine osmolarity of 648 mOsm/kg and urine sodium of 93 mEq/L. His adrenocorticotropic hormone (ACTH) stimulation test was normal. Initial cortisol of 12.5 μg/dL, then 21 μg/dL and 23.7 μg/dL at 30 minute and 60 minute intervals, respectively, after tetracosactide [cosyntropin] administration was noted. Thyroid-stimulating hormone (TSH) was markedly increased at 88.6 IU/mL with total triiodothyronine (TT3) <21 ng/mL, free thyroxine (fT4) 0.10 ng/dL and free triiodothyronine (fT3) <0.5 pg/mL. Atithyroid peroxidase (antiTPO) antibody was 726 IU/mL. A review showed that 1 year ago, his baseline thyroid function tests had shown normal TSH and TT3. Based on clinical and laboratory findings, he was diagnosed with hypothyroidism associated with pomalidomide. He was treated with levothyroxine sodium [levothyroxine]. His pomalidomide was stopped. His hyponatraemia was thought to result from his hypothyroidism. Gradually, his sodium improved to 131 mEq/L on discharge. After 4 weeks, his sodium was 138 mEq/L. After 8 months of discharge, his TSH was 5.06 IU/mL.