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Hypothalamic-pituitary-ovarian axis. Gonadotropin synthesis and release and differential expression are under both positive and negative feedback control
by ovarian steroid and peptide hormones. Ovarian hormones can decrease gonadotropin release both by modulating gonadotropin-releasing hormone
(GnRH) pulse frequency from the hypothalamus and by affecting the ability of GnRH to stimulate gonadotropin secretion from the pituitary itself. Estradiol
enhances luteinizing hormone (LH) and inhibits follicle-stimulating hormone (FSH) release, whereas inhibins A and B (gonadal glycoprotein hormones)
reduce FSH secretion. After ovulation, ovarian progesterone production predominates. Progesterone increases hypothalamic opioid activity and slows
GnRH pulse secretion, favoring FSH production and decreasing LH release. Inhibin B peaks early in the follicular phase, whereas inhibin A peaks in the
Source: Chapter 9. Female Reproductive System, Endocrine Physiology, 4e
midluteal phase. The increasing inhibin B levels in the midfollicular phase act at the pituitary gonadotroph to offset activin signaling and suppress FSH
Molina
PE. Endocrine
Physiology,
4e; 2013
Available
http://mhmedical.com/
Accessed:
05, 2017
biosynthesis Citation:
from early
follicular
phase levels.
The decrease
in inhibin
A atat:the
end of the luteal phase
createsMay
an environment
in which FSH levels can
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again increase. GABA, γ-aminobutyric acid; DA, dopamine; IL-1, interleukin 1; NE, norepinephrine; NPY, neuropeptide Y; Prl, prolactin.