Fellow Jersey Shore University Medical Center Freehold, New Jersey, United States
Introduction : Thyrotropin alfa, also known as recombinant-human thyroid-stimulating hormone (rh-TSH), has emerged as a widely accepted alternative to thyroid hormone withdrawal for whole-body scans, demonstrating comparable outcomes and fewer patient-reported adverse events. We present a patient undergoing a rh-TSH-stimulated iodine-123 (I-123) scan, who developed underreported side effects including elevated transaminases and elevated gonadotropins.
Case(s) Description : This is a 39 year old male with a past medical history of papillary thyroid cancer, status-post total thyroidectomy and radioactive iodine ablation, who underwent a rh-TSH-stimulated I-123 scan as part of routine monitoring. Fatigue and decreased libido prompted additional lab tests, which were inadvertently completed after the rh-TSH injections. His labs showed an appropriate response of TSH of 43.100 mIU/L, while follicle stimulating hormone (FSH) was elevated to 14 mIU/mL and luteinizing hormone (LH) was 8.9 mIU/mL. Prolactin and testosterone remained in the normal range. His liver enzymes were increased significantly including aspartate transaminase (AST) of 393 IU/L and alanine aminotransferase (ALT) of 112 IU/L. One month before rh-TSH, AST was 34 IU/L, and ALT was 39 IU/L. A week later, transaminase levels started declining, returning to normal three months post-treatment, along with FSH and LH.
Discussion : Thyrotropin alfa has proven effective as an exogenous TSH source with potential benefits over traditional withdrawal methods. Studies of laboratory assays have shown potential for cross-over between TSH and FSH, which may play a partial role in this case. Acute liver injury is a known side effect of thyrotoxicosis and hyperthyroidism. However, proposed mechanisms suggest that this is due to increased metabolic demand of hepatocytes, caused by an increase in the biologically active forms of thyroxine (T4) and 3,5,3 triiodothyronine (T3). Elevated liver enzyme levels are not commonly associated with rh-TSH, but in the absence of any other acute etiologies, suggest a potential need to consider the possibility when ordering rh-TSH.
