DƯỢC LÍ Goodman & Gilman's The Pharmacological Basis of Therapeutics 12th, 2010

1166 Estrogens appear to play important developmental
roles in males. In boys, estrogen deficiency diminishes
the pubertal growth spurt and delays skeletal
maturation and epiphyseal closure so that linear growth
continues into adulthood. Estrogen deficiency in men
leads to elevated gonadotropins, macroorchidism, and
increased testosterone levels and also may affect carbohydrate
and lipid metabolism and fertility in some
individuals (Grumbach and Auchus, 1999).
Neuroendocrine Control of the Menstrual Cycle. A neuroendocrine
cascade involving the hypothalamus,
pituitary, and ovaries controls the menstrual cycle
(Figure 40–2). A neuronal oscillator, or “clock,” in the
hypothalamus fires at intervals that coincide with bursts
of gonadotropin-releasing hormone (GnRH) release
into the hypothalamic-pituitary portal vasculature
(Chapter 38). GnRH interacts with its cognate receptor
on pituitary gonadotropes to cause release of luteinizing
hormone (LH) and follicle-stimulating hormone
(FSH). The frequency of the GnRH pulses, which
varies in the different phases of the menstrual cycle,
controls the relative synthesis of the unique β subunits
of FSH and LH.
SECTION V
HORMONES AND HORMONE ANTAGONISTS
arcuate
nucleus
medial
basal
hypothalamus
progesterone
pituitary
hypothalamic
pulse
generator
opioid
NE
dopamine
+
– – + +
GABA
–
GnRH
B
A
Neuronal
Activity
(discharges
per min)
LH
(ng/ml)
D
0
1 2 3 4
TIME (hrs)
GnRH
neuron
pituitary
portal
vasculature
GnRH
C
gonadotrope
estrogen
progesterone
LH / FSH
E
estrogen
progesterone
uterus
ovary
estrogen
progesterone
E
Figure 40–2. Neuroendocrine control of gonadotropin secretion in females. The hypothalamic pulse generator located in the arcuate
nucleus of the hypothalamus functions as a neuronal “clock” that fires at regular hourly intervals (A). This results in the periodic release
of gonadotropin-releasing hormone (GnRH) from GnRH-containing neurons into the hypothalamic-pituitary portal vasculature (B).
GnRH neurons (B) receive inhibitory input from opioid, dopamine, and GABA neurons and stimulatory input from noradrenergic neurons
(NE, norepinephrine). The pulses of GnRH trigger the intermittent release of luteinizing hormone (LH) and follicle-stimulating
hormone (FSH) from pituitary gonadotropes (C), resulting in the pulsatile plasma profile (D). FSH and LH regulate ovarian production
of estrogen and progesterone, which exert feedback controls (E). (See text and Figure 40–3 for additional details.)