triiodothyronine--reverse and Hyperemesis-Gravidarum

To investigate the possible physiological relevance of extra-thyroidal production of reverse T3 (rT3) in hyperemesis gravidarum, measurements of serum rT3, free T3 (FT3), free T4, (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 rT3 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 T3 to rT3 as products of 5'-monodeiodination of thyroxine in hyperemesis gravidarum. Because reverse T3 is physiologically inactive a control mechanism may be postulated wherein T3 production is minimized, thereby reducing weight loss and lipolysis in patients with hyperemesis gravidarum.

Topics: Fatty Acids, Nonesterified; Female; Gestational Age; Humans; Hyperemesis Gravidarum; Lipolysis; Pregnancy; Thyroxine; Triiodothyronine, Reverse; Weight Loss

Thyroid function and pituitary responsiveness to TRH were studied in patients with hyperemesis gravidarum. Serum T3 and T4 concentrations were normal. Serum TBG levels in hyperemesis were normal for gestation, and the T4:TBG ratio was in the euthyroid range. In all patients a normal TSH response to TRH was found. Mean serum rT3 concentration was increased by 31% as compared to a control group of normal pregnant women (P less than 0.001). The data suggest that in patients with hyperemesis gravidarum there is: (a) normal function of the thyroid gland and pituitary-thyroid axis, (b) an enhanced peripheral conversion of T4 to rT3.

Topics: Adult; Female; Humans; Hyperemesis Gravidarum; Pituitary Gland; Pregnancy; Thyroid Gland; Thyrotropin; Thyrotropin-Releasing Hormone; Thyroxine; Thyroxine-Binding Proteins; Triiodothyronine; Triiodothyronine, Reverse