This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Forhead, A. J. Articles by Fowden, A. L. Search for Related Content PubMed PubMed Citation Articles by Forhead, A. J. Articles by Fowden, A. L.

Differential Effects of Maternal Dexamethasone Treatment on Circulating Thyroid Hormone Concentrations and Tissue Deiodinase Activity in the Pregnant Ewe and Fetus

Department of Physiology, Development and Neuroscience (A.J.F., J.K.J., D.S.G., D.A.G., A.L.F.), University of Cambridge, Cambridge CB2 3EG, United Kingdom; and Department of Internal Medicine (E.K., T.J.V.), Erasmus Medical Center, Rotterdam, The Netherlands

Address all correspondence and requests for reprints to: Dr. Alison J. Forhead, Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom. E-mail: ajf1005{at}cam.ac.uk.

Clinically, treatment of pregnant women at risk of preterm delivery with synthetic glucocorticoids accelerates fetal maturation. This study investigated the effect of maternal dexamethasone treatment, in clinically relevant doses, on plasma thyroid hormone concentrations and tissue deiodinase activities (D1, D2, and D3) in ewes and their fetuses. From 125 d of gestation (term 145 ± 2 d), pregnant ewes were injected twice im with either saline (2 ml of 0.9% NaCl, n = 11) or dexamethasone (2 x 12 mg in 2 ml of saline, n = 10) at 24-h intervals. Maternal dexamethasone treatment increased plasma T₃ and reverse T₃ (rT₃), but not T₄, concentrations in the fetuses. In the dexamethasone-exposed fetuses, hepatic D1 activity was higher, and renal and placental D3 activities were lower, than in the saline-exposed fetuses. In the ewes, plasma concentrations of T₃ and T₄ were reduced, and rT₃ increased, by dexamethasone treatment without any change in tissue deiodinase activity. Therefore, maternal dexamethasone treatment has different effects on the thyroid hormone axis of the pregnant ewe and fetus. In the fetus, the dexamethasone-induced rise in circulating T₃ may be due to both increased hepatic production of T₃ from T₄, and reduced clearance of T₃ by the kidney and placenta. Changes in T₃ bioavailability may mediate some of the maturational effects of antenatal glucocorticoid treatment in the preterm fetus.

This article has been cited by other articles:

				A. J. Forhead, S. Cutts, P. A. Matthews, and A. L. Fowden Role of thyroid hormones in the developmental control of tissue glycogen in fetal sheep near term Exp Physiol, October 1, 2009; 94(10): 1079 - 1087. [Abstract] [Full Text] [PDF]

				A. L. Fowden and A. J. Forhead Hormones as epigenetic signals in developmental programming Exp Physiol, June 1, 2009; 94(6): 607 - 625. [Abstract] [Full Text] [PDF]