Alterations in the homeostasis of biomolecules and multiple organ dysfunctions associated with cigarette smoke may suggest a dose dependent mechanism. This study assessed the triiodothyronine (T3), thyroxine (T4), thyrotropin (TSH), calcium (Ca), albumin and vitamin C levels in relation to smoking pack years (SPY) in male active smokers. Ninety consenting males (18-60 yr) comprising of moderate smokers (n=26), light smokers (n=24) and non-smokers (n=40) were studied. Triiodothyronine, thyroxine, TSH and cotinine were determined by ELISA, calcium, albumin and vitamin C by colorimetry. The BMI, calcium, albumin, vitamin C and TSH were higher and cotinine, T3 and T4 lower in non-smokers compared to moderate and light smokers. Light smokers had higher BMI, vitamin C and TSH and lower cotinine, T3 and T4 compared to moderate smokers. In smokers, cotinine correlated positively with SPY (r = 0.838, P = 0.000), T3 (r=0.339, P = 0.005), T4 (r = 0.443, P = 0.001) and negatively with BMI (r = -0.478, P = 0.000), vitamin C (r=-0.407, P=0.003) and TSH (r = -0.510, P = 0.000) while SPY correlated positively with T3 (r=0.586, P = 0.000), T4 (r = 0.608, P = 0.000) and negatively with BMI (r = -0.597, P = 0.000), vitamin C (r = -0.599, P = 0.000), albumin (r = -0.281, P = 0.048) and TSH (r = -0.578, P = 0.000). Cigarette smoking and increasing smoking pack year may be associated with abnormal thyroid function and altered calcium, albumin and vitamin C homeostasis. Manuscript profile