ACE and hypertensive disorder: ACE deletion/insertion polymorphism was significantly associated with essential hypertension in the allele contrast model (P = 0.01) showing significant heterogeneity (P = 0.0001) and no publication bias (P = 0.32); the recessive model (P = 0.03) showing significant heterogeneity (P = 0.0001) and no publication bias (P = 0.46); and the dominant model (P = 0.032 and with non-significant heterogeneity (P = 0.12) or publication bias (P = 0.28); and the homozygote codominant model (P = 0.018) with significant heterogeneity (P = 0.008) and no publication bias (P = 0.30).