Severity of hyperemesis gravidarum correlates with serum levels of reverse T3

To investigate the possible physiological relevance of extra-thyroidal production of reverse T-3 (rT(3)) in hyperemesis gravidarum, measurements of serum rT(3), free T-3 (FT3), free T-4, (FT4), and nonesterified fatty acids (NEFA) were correlated with weight loss of hyperemetic women. All the thyroid hormones, NEFAs and weight loss were significantly higher in hyperemesis gravidarum than in control subjects, and also higher than in those with milder symptoms of morning sickness (p < 0.05). Elevations of FT3, FT4 and NEFAs correlated with the extent of weight loss, the latter taken as the index of the severity of hyperemesis gravidarum (p < 0.05). Only rT(3) correlated with both weight loss and the rate of lipolysis, as reflected by elevations of NEFAs (p < 0.05). The data are consistent with a shift from T-3 to rT(3) as products of 5'-monodeiodination of thyroxine in hyperemesis gravidarum. Because reverse T-3 is physiologically inactive a control mechanism may be postulated wherein T-3 production is minimized, thereby reducing weight loss and lipolysis in patients with hyperemesis gravidarum.