Maternal-to-fetal transfer of thyrotropin-releasing hormone in vivo*,**

https://doi.org/10.1016/S0002-9378(98)80011-2Get rights and content

Objective: Our purpose was to determine the transplacental transfer of thyrotropin-releasing hormone at the time of fetal blood sampling.

Study Design: Four hundred micrograms of thyrotropin-releasing hormone was given intravenously to 13 pregnant women between 24 and 35 weeks' gestation and maternal-to-fetal transfer of thyrotropin-releasing hormone was determined at fetal blood sampling 1 to 93 minutes later. The fetal thyrotropic response to thyrotropin-releasing hormone was determined by measuring thyroid-stimulating hormone, thyroxine, and prolactin. For comparison, endogenous fetal and maternal levels of thyrotropin-releasing hormone, thyroidstimulating hormone, thyroxine, and prolactin levels were determined in a further 20 patients undergoing fetal blood sampling between 19 and 35 weeks' gestation. The concentration of thyrotrophin-releasing hormone was measured by radioimmunoassay and thyroid-stimulating hormone, thyroxine, and prolactin by chemiluminescence assay.

Results: Thyrotropin-releasing hormone was undetectable in the maternal circulation, whereas endogenous levels were detectable in the fetus from 19 weeks' gestation (median 150; range 50 to 276 pmol/L) and did not correlate with gestational age. After thyrotropin-releasing hormone injection as an intravenous bolus, peak levels in the mother were attained at 3 minutes (50,000 pmol/L). Maximal transplacental transfer of thyrotropin-releasing hormone occurred within 5 minutes of maternal administration but accounted in fetal blood for only 0.01% of initial dose administered (median 250; 30 to 550 pmol/L). Thyrotropin-releasing hormonestimulated fetal peak thyroid-stimulating hormone levels occurred within 13 minutes and were higher than maternal values (p<0.001). There was no change in fetal prolactin level with thyrotropin-releasing hormone therapy.

Conclusion: Although maternally administered thyrotropin-releasing hormone crosses the placenta sparingly, it still elicits a thyroid-stimulating hormone but not a prolactin response in the human fetus.

References (25)

  • BajoriaR et al.

    Transfer of heparin across the human perfused placental lobule

    J Pharm Pharmacol

    (1992)
  • BajoriaR et al.

    Maternal-fetal transfer of warfarin across an in vitro model of perfused placenta: effect of albumin binding

    Br J Haematol

    (1993)
  • Cited by (20)

    • Pregnancy and the fetus

      2020, Handbook of Diagnostic Endocrinology
    • The forgotten effects of thyrotropin-releasing hormone: Metabolic functions and medical applications

      2019, Frontiers in Neuroendocrinology
      Citation Excerpt :

      During pregnancy low amounts of maternal TRH reach the fetus because the peptide is enzymatically cleaved (Bajoria et al., 1996). When TRH is administered to pregnant women between 19th and 35th of gestation, fetal TSH secretion but not PRL secretion increases (Bajoria et al., 1998). When TRH is administered later, TSH and PRL levels increase in the fetal circulation (Ballard et al., 1992a).

    • Endocrine Diseases of Pregnancy

      2019, Yen &amp; Jaffe's Reproductive Endocrinology: Physiology, Pathophysiology, and Clinical Management: Eighth Edition
    • Endocrine Diseases of Pregnancy

      2013, Yen and Jaffe's Reproductive Endocrinology: Seventh Edition
    • Endocrine diseases of pregnancy

      2009, Yen &amp; Jaffe's Reproductive Endocrinology: Expert Consult - Online and Print
    • Endocrine Diseases of Pregnancy

      2009, Yen &amp; Jaffe's Reproductive Endocrinology
    View all citing articles on Scopus
    *

    Supported by a project grant from Action Research.

    **

    Reprints not available from the authors.

    View full text