But in another study by Rasheed et al. about the effect of heroin on thyroid hormones, T3 level of heroin-dependents has been slightly higher than that of the control group, while TSH and T4 levels did not show significant difference between the two groups[9] Dogar et al. have reported significant elevated T3 and decreased T4 levels in the serum of substance abusers compared to the control group[24]. The gene discussed is TG; the disease is substance abuse.