Comparison of progesterone and glucocorticoid receptor binding and stimulation of gene expression by progesterone, 17-alpha hydroxyprogesterone caproate, and related progestins

Am J Obstet Gynecol. 2007 Dec;197(6):599.e1-7. doi: 10.1016/j.ajog.2007.05.024.


Objective: This study was undertaken to determine whether the reduction in premature birth attributable to 17-alpha hydroxyprogesterone caproate occurs because of a greater affinity for progesterone or glucocorticoid receptors or by enhanced stimulation of progestogen responsive genes when compared with progesterone.

Study design: We performed competitive steroid hormone receptor binding assays using cytosols expressing either recombinant human progesterone receptor-A or -B or rabbit uterine or thymic cytosols. We used 4 different carcinoma cell lines to assess transactivation of reporter genes or induction of alkaline phosphatase.

Results: Relative binding affinity of 17-alpha hydroxyprogesterone caproate for recombinant human progesterone receptor-B, recombinant human progesterone receptor-A, and rabbit progesterone receptors was 26-30% that of progesterone. Binding of progesterone to rabbit thymic glucocorticoid receptors was weak. 17-alpha hydroxyprogesterone caproate was comparable to progesterone in eliciting gene expression in all cell lines studied.

Conclusion: Binding to progesterone receptors, glucocorticoid receptors, or expression of progesterone-responsive genes is no greater with 17-alpha hydroxyprogesterone caproate than with progesterone. Other mechanisms must account for the beneficial effect of 17-alpha hydroxyprogesterone caproate on preterm birth rates.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • 17 alpha-Hydroxyprogesterone Caproate
  • Cell Line, Tumor
  • Female
  • Gene Expression
  • Humans
  • Hydroxyprogesterones / pharmacology
  • Pregnancy
  • Progesterone / pharmacology
  • Progestins / pharmacology*
  • Receptors, Glucocorticoid / drug effects
  • Receptors, Glucocorticoid / genetics*
  • Receptors, Glucocorticoid / metabolism*
  • Receptors, Progesterone / drug effects
  • Receptors, Progesterone / genetics*
  • Receptors, Progesterone / metabolism*


  • Hydroxyprogesterones
  • Progestins
  • Receptors, Glucocorticoid
  • Receptors, Progesterone
  • 17 alpha-Hydroxyprogesterone Caproate
  • Progesterone