Schematic diagram of idealized regimens using exogenous gonadotropins for fertility induction. A. Step-up regimen for ovulation induction. After menses, daily injections of gonadotropin (75 IU) are started. Follicle maturation is assessed by serial measurement of plasma estradiol and follicle size, as discussed in the text. If an inadequate response is seen, the dose of gonadotropin is increased to 112 or 150 IU/day. When one or two follicles have achieved a size of ≥17 mm in diameter, final follicle maturation and ovulation are induced by injection of human chorionic gonadotropin (hCG). Fertilization then is achieved at 36 hours after hCG injection by intercourse or intrauterine insemination (IUI). If more than two mature follicles are seen, the cycle is terminated and barrier contraception is used to avoid triplets or higher degrees of multifetal gestation. B. Long protocol for ovarian hyperstimulation using gonadotropin-releasing hormone (GnRH) agonist to inhibit premature ovulation, followed by in vitro fertilization (IVF). After the GnRH agonist has inhibited endogenous secretion of gonadotropins, therapy with exogenous gonadotropins is initiated. Follicle maturation is assessed by serial measurements of plasma estradiol and follicle size by ultrasonography. When three or more follicles are ≥17 mm in diameter, then ovulation is induced by injection of hCG. At 32-36 hours after the hCG injection, the eggs are retrieved and used for IVF. Exogenous progesterone is provided to promote a receptive endometrium, followed by embryo transfer at 3-5 days after fertilization. C. Protocol for ovarian hyperstimulation in an IVF protocol using a GnRH antagonist. The cycle duration is shorter because the GnRH antagonist does not induce a transient flare of gonadotropin secretion that might disrupt the timing of the cycle, but many other elements of the cycle are analogous to those in B. IU, intrauterine. Source: Contraception and Pharmacotherapy of Obstetrical and Gynecological Disorders, Goodman & Gilman's: The Pharmacological Basis of Therapeutics, 12e Citation: Brunton LL, Chabner BA, Knollmann BC. Goodman & Gilman's: The Pharmacological Basis of Therapeutics, 12e; 2011 Available at: http://accessmedicine.mhmedical.com/DownloadImage.aspx?image=/data/Books/1613/bru12_ch66_f001.png&sec=102164813&BookID=1613&ChapterSecID=102164759&imagename= Accessed: October 05, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved