TG and thyrotoxicosis: 4 As pregnancy progresses, changes in albumin and free fatty acid concentrations can affect the binding of thyroid hormones to its carrier proteins resulting in lower serum levels of free T3 and free T4. 5 Studies have shown that patients with a higher hCG concentration, such as those experiencing hyperemesis, may have an increased severity of vomiting and degree of thyroid stimulation.6 Most hyperemesis gravidarum patients who develop thyrotoxicosis have a transient course and do not require anti-thyroid medication.3