Himalaya Livline | Vol 6 | No. 4 | May–Aug 2023 | 15 Effect of Hyperthyroidism on Liver Function Normal biosynthesis and functioning of the thyroid hormones thyroxine (T4), 3,5,3′-triiodothyronine (T3), and thyroid-stimulating hormone are critical for maintaining metabolic homeostasis in the body. An intricate relationship is known to exist between the thyroid gland and the liver in health and diseases. Thus, any disturbance in the metabolism of the thyroid hormones can affect liver function. Hyperthyroidism, a form of thyrotoxicosis, is caused by excessive production and secretion of T3 and T4 hormones into systemic circulation. Scientific evidence indicates that hyperthyroidism has a significant effect on the biosynthesis and functioning of liver enzymes, and thereby contributes to liver dysfunction. A recent meta-analysis reveals that 55% to 60% of the patients with untreated hyperthyroidism show at least one abnormality in the liver function biomarker levels. The highest abnormality was found in the level of alkaline phosphatase (ALP), followed by that of alanine transaminase, γ-glutamyl transferase (GGT), aspartate transaminase, and total bilirubin. Liver Injury Patterns A spectrum of pathological changes from focal necrosis with steatosis to cirrhosis can ensue from untreated hyperthyroidism. Several direct and indirect mechanisms that are involved in thyrotoxicosis-associated liver dysfunction exhibit either a hepatic pattern or a cholestatic pattern. Hepatic pattern: Prolonged exposure to excessive thyroid hormones, hypermetabolic state, accelerated liver glycogen and protein decomposition, autoimmunity, and underlying liver diseases may trigger hepatic dysfunction in patients with thyrotoxicosis. Cholestatic pattern: Hepatic dysfunction in Graves’ disease is predominantly a cholestatic pattern. Nonspecific histologic changes in the hepatocytes, centrilobular intrahepatic cholestasis, jaundice, and predominant elevation in ALP (due to increased osteoblastic activity) and GGT levels also trigger hepatic dysfunction in patients with thyrotoxicosis. Therefore, the examination of liver function upon diagnosis of hyperthyroidism is important to identify any hepatic abnormalities. Sources: Yorke E. Clin Med Insights Endocrinol Diabetes. 2022;15:1–3. Malik R, Hodgson H. QJM Int J Med. 2002;95(9):559–569. The Liver and the Body A spectrum of pathological changes from focal necrosis with steatosis to cirrhosis can result from untreated hyperthyroidism.
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