LAUSR

Introduction Thyroxine plays a significant role in hepatic and renal physiology and thyroid dysfunction can therefore produce a wide range of metabolic disturbances. We report two severe hypothyroid paediatric patients presenting with hepatic and renal dysfunction at diagnosis. Case 1 A 12-year-old male in foster care for psychosocial issues presented with 1 year history of lethargy, growth failure, and hair loss. He was noted to have severe hypothyroidism with Free T4 of 0.5 pmol/L (NR: 12.1–22.2), TSH >99.9 Mu/L (0.3–4.2), raised creatinine of 119 umol/L (40–68), urea of 9.5, raised ALT of 126 U/L (10–60), and raised CPK of 1273 U/L (4–320). He was commenced on thyroxine, with his LFTs, creatinine, and CPK normalizing within 6 weeks. Case 2 A 15-year-old female presented with 3 year history of sub-optimal growth and lethargy. She was profoundly hypothyroid with TSH of 100 Mu/L (0.3–4.2), FT4 of 0.8 pmol/L (12–22), creatinine of 97 umol/L (15–70), and normal ALT. Serum creatinine and thyroid function normalized within 6 weeks of initiation of thyroxine. Discussion There are many postulated mechanisms for the effect of hypothyroidism on renal and hepatic function. The role of hypothyroidism in liver dysfunction is not well understood. Thyroid hormones enhance the metabolism of bilirubin by increasing the activity of the UDP-glucuronosyltransferase enzyme. Hypometabolism due to hypothyroidism can cause elevated cholesterol levels, non-alcoholic fatty liver disease, and abnormalities of AST and ALT. Thyroxine also plays a role in bilirubin and bile acid secretion, and cholestatic jaundice has been reported in hypothyroidism. Hypothyroidism affects the kidney both functionally and structurally. Thyroid hormones regulate renal blood flow and hypothyroidism can be associated with pathological glomerular changes. In hypothyroidism, the glomerular filtration rate (GFR) can be reduced due to decreased sensitivity to beta-adrenergic stimuli. There is a reduction in chloride reabsorption, resulting in a reduction of renin-angiotensin-aldosterone system (RAAS) activity. Hypothyroidism is also associated with myopathy and rhabdomyolysis, which can further contribute to kidney damage. Conclusion Severe hypothyroidism can be associated with transient hepatic and renal dysfunction, which resolve with initiation of levothyroxine. It appears that delayed diagnosis of hypothyroidism may have contributed to these transient abnormalities.