B3GAT2 and hypothyroidism: This clinical study reports an euthyroid patient on levothyroxine treatment who developed refractory hypothyroidism with reduced levothyroxine absorption following treatment with apalutamide, suggesting that apalutamide decreases the digestive absorption of levothyroxine, in addition to stimulating the activity of hepatic UDP-glucuronosyltransferase (3), explaining the higher prevalence of hypothyroidism in patients previously treated with levothyroxine.