Thyrotropin-releasing hormone: does two hundred micrograms provide effective stimulation to the preterm fetal pituitary gland compared with four hundred micrograms?
OBJECTIVE
Our purpose was to compare the response of the fetal pituitary-thyroid axis to 200 and 400 micrograms of thyrotropin-releasing hormone administered to the mother immediately before delivery with a control group.


METHODS
A randomized controlled trial was conducted of 26 women at gestational ages between 24 weeks and 33 weeks 6 days who had received one or more doses of betamethasone who were expected to be delivered within 1 to 4 hours. Women received either 200 or 400 micrograms of thyrotropin-releasing hormone or were in the control group.


RESULTS
Thyroid-stimulating hormone determinations on cord blood had a higher mean level in both treatment groups compared with the control group. No differences were seen in cord blood results between the two treatment groups for thyroid-stimulating hormone, thyroxine, triiodothyronine, free thyroxine, free triiodothyronine, and prolactin levels. The only other differences found were in a higher level in total thyroxine and a lower level of free thyroxine in the 400 micrograms thyrotropin-releasing hormone group compared with the 200 micrograms group in the 48-hour blood determinations.


CONCLUSIONS
Both 200 and 400 micrograms of thyrotropin-releasing hormone provided fetal pituitary stimulation, as reflected in fetal thyroid-stimulating hormone levels in cord blood, and both gave significantly higher levels compared with a control group.
Crowther
C
C
Department of Obstetrics and Gynaecology, University of Adelaide, Australia.
Haslam
R
R
Hiller
J
J
McGee
T
T
Ryall
R
R
Robinson
J
J
D000328:Adult; D004305:Dose-Response Relationship, Drug; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005865:Gestational Age; D006801:Humans; D010902:Pituitary Gland / Q000196:embryology* / Q000502:physiology; D011247:Pregnancy; D011388:Prolactin / Q000097:blood; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D013972:Thyrotropin; D013974:Thyroxine