519
Hypothalamic-Pituitary-
Ovarian-Uterine Axis
Chapter 52
Chelsea Ward, MD
HYPOTHALAMUS
❍ What structure in the hypothalamus produces the most gonadotropin-releasing hormone (GnRH)?
Arcuate nucleus in the medial basal hypothalamus.
❍ What is the name of the bundle of nerve cells that carry GnRH to the anterior pituitary?
Tuberoinfundibular tract.
❍ What is the half-life of GnRH?
2 to 4 minutes.
❍ How does the pulsatility of GnRH vary in the menstrual cycle?
Frequency is more rapid in follicular phase, 1 pulse per hour; slower in luteal phase, 1 pulse in 2 to 3 hours.
❍ What can altered frequency and/or amplitude lead to?
Anovulation (hypothalamic amenorrhea).
❍ Amplitude and frequency of GnRH secretion is regulated by which hormones?
Ovarian hormones: Estradiol and progesterone
Neurotransmitters: Dopamine, norepinephrine, and serotonin
Neuromodulators: Prostaglandins and opioids
Brain peptides: Neuropeptide Y, melatonin, and leptin
❍ What is the effect of norepinephrine on GnRH release?
Stimulatory effect.
❍ What are the effects of dopamine and serotonin on GnRH release?
They inhibit GnRH release.