Resumen

GUERRERO-LOBO, Carmen Lidia. Elevated Serum Creatinine in Hypothyroidism: Myopathy or Real Nephropathy ? Classification Proposal. Acta méd. costarric [online]. 2009, vol.51, n.1, pp.44-48. ISSN 0001-6002.

Background: In patients with hypothyroidism is possible to find an increased serum creatinine not only due to renal failure but to myopathy in presence of normal renal function. Two patients, each representing 1 type of a proposed classification regarding thyroid dysfunction and abnormal creatinine are presented, in order to communicate this relationship, until now based on isolated reports. The first individual had an increased serum creatinine with normal renal function due to hypothyroid myopathy (type 1). Rhabdomyolysis related to this myopathy is pointed as a cause of acute renal failure. The 2nd patient had an increased serum creatinine with abnormal kidney function (type 2), which improved when he became euthyroid after levothyroxine administration. The diagnosis of hypothyroidism is often missed in patients with altered renal function, if it becomes evident and is properly treated the renal function will improve. As is known hypothyroidism causes hypercholesterolemia, if such patient unknowingly receives statins or gemfibrozil, severe rhabdomyolysis and renal falilure may occur, as reported in the literature. The 3d category of the classification is the occurrence of nephrotic syndrome in hypothyroid patients who discontinue T4 treatment due to thyroid cancer for further studies or by patient non adherence, developing significant proteinuria few months later. Kidney biopsy lesions vary from membranous glomerulopathy to membranoproliferative glomerulonephritis. These findings will resolve with the administration of levothiroxine, without glucocorticoids. However patients with nephrotic syndrome related to Hashimoto thyroiditis will improve with glucocorticoids. Conclusion: 1. TSH must be requested when: a) There is an increased serum creatinine or hypercholesterolemia without a clear cause. b) In patients with rabdomyolysis or acute renal failure with increased CK since it may be secondary to hypothyroid myopathy. 2. Serum creatinine should be requested in hypothyroid patients who discontinue levothyroxine for any reason or are using amiodarone. 3) Proteinuria within the nephrotic range in a hypothyroid patient who has discontinued levothiroxine will have a different response to treatment depending of the cause (if it is autoimmune it will respond to glucorticoids and if is not, will respond to levothyroxine.

Palabras clave : serum creatinin; renal function; glomerulopathy; hypothyroidism; polymyositis; rabdomyolysis.

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