Key words: Chronic kidney disease, Glomerular filtration rate, Free Thyroxin, Thyrotrophin. INTRODUCTION Chronic kidney disease is a global public health threat associated with an alarming increase in morbidity and mortality. The importance is the worldwide increase in 1'2 its incidence and prevalence . The major outcomes of chronic kidney disease regardless of cause include progression to kidney failure, complications of decreased kidney function and cardiovascular 3 disease . Chronic kidney disease (CKD) is defined as kidney damage or glomerular filtration rate 2 <60ml/min/1.73m for 3 months or more, irrespective of cause. Glomerular filtration rate can be estimated from calibrated serum creatinine and 3 estimating equation like Cockcroft-Gault formula . The interactions between kidney and thyroid functions are known for years. The decline of kidney function is accompanied by changes in the synthesis, secretion, metabolism and elimination of thyroid hormone. Both hypothyroidism and hyperthyroidism affect renal blood flow, glomerular filtration rate, tubular function, electrolytes homeostasis, electrolyte pump functions 4 and kidney structure In the absence of thyroid . disease, patients with non-thyroid illness frequently have changes in serum levels of thyroid hormones that 5 may suggest thyroid dysfunction . Uraemic patients have an increased thyroid volume compared with subjects with normal renal function and a higher prevalence of goiter, mainly in woman. Also, thyroid nodules and thyroid carcinoma are more common in uraemic patients than in the general population. Chronic kidney disease affects both hypothalamus- pituitary- thyroid axis and thyroid hormone peripheral Dr. Muhammad Asif, Mr. Muhammad Akram, Mr. Atif Ullah. CHRONIC KIDNEY DISEASE; CORRELATION BETWEEN FREE THYROXIN, THYROTROPHIN AND GLOMERULAR FILTRATION RATE ORIGINAL PROF-2189 Professional Med J 2013;20(4): 506-512. 506 www.theprofesional.com Asif M, Akram M, Ullah A. Chronic kidney disease; correlation between free thyroxin, thyrotrophin and glomerular filtration rate. Professional Med J 2013;20(4): 506-512. Article Citation 2 ABSTRACT… Introduction: Chronic kidney disease (CKD) is defined as kidney damage or glomerular filtration rate <60ml/min/1.73m for 3 months or more, irrespective of cause. Objective: To measure glomerular filtration rate, free thyroxin, thyrotrophin in chronic kidney disease patients and to find out the correlation between glomerular filtration rate, free thyroxin and thyrotrphin in these patients. Study Design: Cross sectional analytical study. Setting: Post Graduate Medical Institute (PGMI), Lahore General Hospital (LGH) Lahore. Period: 6 months (Nov 2011 to April 2012). Material and Methods: Sixty five patients were included in the study. Serum Creatinine, TSH and Free T4 were measured; Thyroid function tests TSH, FT4 were measured in these chronic kidney disease patients through enzyme linked immunosorbant assay method. GFR was calculated through Cock-croft-Gualt formula and the relevant data was entered in a predesigned Proforma. Results: In the study total 65 chronic kidney disease patients were taken. Out of which thirty six (55.4%) were male and twenty nine (44.6%) were female. Thirty five (53.8%) CKD patients whose TSH levels were above the normal limit while in the remaining patients the TSH values were in the normal range. Eight patients (12.3%) out of sixty five patients in whom FT4 values were below the normal limit while in the remaining fifty seven patients (87.6%) FT4 values were within the reference range. Those eight patients whose FT4 was below the normal value, their TSH values were above the normal value too. Thirty five patients, whose TSH levels were above the normal 2 limit, their mean age was 50.60± 11.95, mean serum creatinine was 4.73± 2.94 mg/dl, mean GFR was 22.17± 12.48 ml/min/1.73m , mean TSH was 6.68± 0.87 mIU/L and mean FT4 was 0.97± 0.35 ng/dl. The p-value of TSH was < 0.001 and FT4 was < 0.05 in comparing with normal. Glomerular filtrations rate with TSH and FT4 the co-efficient of correlation (r) value for 35 patients to be – 0.713 and 0.47 for TSH and FT4 respectively. Their p- values were 0.000 and 0.004 respectively, and p < 0.001 collectively. This was found to be statistically significant. Linear regression line was obtained between GFR and TSH and GFR and FT4 in CKD patients. Conclusions: From these correlation studies I concluded that the chronic kidney disease is associated with biochemical thyroid dysfunctions causing most commonly subclinical hypothyroidism.