These include:
Decreased myometrial activity with progesterone in vitro but no effect or increased myometrial activity with OHPC
Prevention of cervical ripening with progesterone but unknown effect with OHPC
A non-significantly increased rate of stillbirth and miscarriages with OHPC (in one study)
A possibly increased incidence of gestational diabetes with OHPC (increased in two studies, no difference in one study) but no such effect with progesterone
A significantly increased risk of perinatal adverse effects such as fetal loss and preterm delivery in multiple gestations with OHPC (in two studies)Differences in the metabolism of progesterone and OHPC and differences in the formation and activities of metabolites may be responsible for or involved in these observed biological and pharmacological differences. Progesterone is metabolized by 5α- and 5β-reductases, 3α- and 3β-hydroxysteroid dehydrogenases, and 20α- and 20β-hydroxysteroid dehydrogenase in various tissues. In target tissues, particularly the cervix and myometrium, these enzymes regulate local progesterone concentrations and can activate or inactivate progesterone signaling. In addition, these enzymes catalyze the formation of metabolites of progesterone such as 5β-dihydroprogesterone and allopregnanolone, which signal through their own non-genomic receptors such as membrane progesterone receptors and the GABAA receptor and have their own important effects in pregnancy. As examples, 5β-dihydroprogesterone has been found to play an important role in suppressing myometrial activity while allopregnanolone has potent sedative and anesthetic effects in the mother and especially the fetus and is involved in fetal nervous system development.
Histrelin acetate, sold under the brand names Vantas and Supprelin LA among others, is a nonapeptide analogue of gonadotropin-releasing hormone (GnRH) with added potency. When present in the bloodstream, it acts on particular cells of the pituitary gland called gonadotropes. Histrelin stimulates these cells to release luteinizing hormone and follicle-stimulating hormone. Thus it is considered a gonadotropin-releasing hormone agonist or GnRH agonist. Medical uses
Histrelin is used to treat hormone-sensitive cancers of the prostate in men and uterine fibroids in women. In addition, histrelin has been proven to be highly effective in treating central precocious puberty in children.It is available as a daily intramuscular injection. Histrelin is also available in a 12-month subcutaneous implant (Vantas) for the palliative treatment of advanced prostate cancer, since 2005 in the US, and since Jan 2010 in the UK. A 12-month subcutaneous implant (Supprelin LA) for central precocious puberty (CPP) was approved on May 3, 2007 by the U.S. Food and Drug Administration. Histrelin can be part of the primary care protocol in transgender children/youth, which is an off-label use in the USA and the UK, and is used in suppressing cis-sex puberty, until the patient is ready to begin cross-sex hormonal therapy. It is also sometimes prescribed to transgender adults who benefit from having their sex hormone production halted. Side effects
Side effects are mainly due to low testosterone levels and include headache, hot flashes, reduced libido, and erectile dysfunction.