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Abstract Background and Objectives: The hyperthyroidism, caused in Pregnancy, may Leads to nausea and vomiting. The aim of this study was to establish the relationship between the serum thyroid stimulating hormone (TSH) and thyroxin. (T4), which reflect thyroid function assessment, with nausea and vomiting, among pregnant women in early pregnancy. Material and Methods: the Subjects of this Case- Control Study were the pregnant women referred to routine laboratory investigations. We Compared 60 pregnant women without nausea and Vomiting with 60 pregnant women with nausea and vomiting in Gorgan, Iran. Results: The results Show that there is an increased level of T4 among 34 subjects (56.6 %) with nausea and vomiting compared to 20 Subjects (33.3 %) of women without nausea and vomiting. The mean of T4 in Case and Control group is 11:30±2.8 and 10.26±2.4hg/dl. This difference is Statistically Significant. (p<0.05). TSH level is nearly the same in both groups. Conclusion: These data suggest that there is a role for elevated T4 in nausea and vomiting among pregnant women, in early pregnancy. Key words: Pregnant women, nausea and vomiting, thyroid stimulating hormone, thyroxin.