During early pregnancy, many women are affected with severe sickness in the morning, that is hyperemesis gravidarum (HG), which represents extreme vomiting in pregnancy. Among HG women, about 66–73% had severe HG and the presence of elevated thyroid function. Data collected from the subjects showed the association of temporary hyperthyroidism with severe morning sickness in our Saveetha Medical Hospital. The pregnancy unique quantification of emesis (PUQE) score helps in assessing the rigorousness of nausea and vomiting during pregnancy. The total sample size was 260 antenatals, out of which 11 were hyperemesis, this is a cross-sectional study and the study period was between June and August 2023. Gestational transient hyperthyroidism prevalence was 1.92%. In our study, we have found that there is a significant relation between the rigorousness of PUQE score with hypocalcemia and we did not find any statistically significant relationship between transient hyperthyroidism and pregnancy. The level of free thyroxine (T4) and thyroid-stimulating hormone (TSH) in transient hyperthyroid women was found to be normal at 20 weeks of gestation. Thus, transient hyperthyroidism in pregnancy was not significantly linked with the rigorousness of the PUQE score. Hence, it is not necessary to test for thyroid function in pregnant women with transient hyperthyroidism unless they have a clinical presentation of hyperthyroidism.