A LITTLE BACKGROUND
The hypothalamus is an area of the brain
that produces the "controlling" hormones. These
hormones regulate body processes such as metabolism, and
control the release of hormones from glands like the thyroid,
the adrenals and the gonads (testes or ovaries).
Ref: http://www.nlm.nih.gov/medlineplus/ency/imagepages/9417.htm
Hormones of the Hypothalamus
The hypothalamus is a region of the brain. It secretes a
number of hormones.
• Thyrotropin-releasing hormone (TRH)
• Gonadotropin-releasing hormone (GnRH)
• Growth hormone-releasing hormone (GHRH)
• Corticotropin-releasing hormone (CRH)
• Somatostatin
• Dopamine
Two other hypothalamic hormones:
• Antidiuretic hormone (ADH) and
• Oxytocin
travel in neurons to the posterior lobe of the pituitary
where they are released into the circulation.
• Thyrotropin-releasing
hormone (TRH)
TRH is a tripeptide (GluHisPro).
When it reaches the anterior lobe of the pituitary it stimulates
the release there of
• thyroid-stimulating hormone (TSH)
• prolactin (PRL)
• Gonadotropin-releasing
hormone (GnRH)
GnRH is a peptide of 10 amino acids. Its secretion at the
onset of puberty triggers sexual development.
Primary Effects Secondary Effects
FSH and LH Up estrogen and progesterone Up (in females)
testosterone Up (in males)
After puberty, a hyposecretion of GnRH may result from
• intense physical training
• anorexia nervosa
Synthetic agonists of GnRH are used to treat
• inherited or acquired deficiencies of GnRH secretion.
• prostate cancer. In this case, high levels of the
GnRH agonist
• reduces the number of GnRH receptors in the pituitary,
which
• reduces its secretion of FSH and LH, which
• reduces the secretion of testosterone, which
• reduces the stimulation of the cells of the prostate.
• Growth
hormone-releasing hormone (GHRH)
GHRH is a mixture of two peptides, one containing 40 amino
acids, the other 44.
As its name indicates, GHRH stimulates cells in the anterior
lobe of the pituitary to secrete growth hormone (GH).
• Corticotropin-releasing
hormone (CRH)
CRH is a peptide of 41 amino acids.
As its name indicates, its acts on cells in the anterior
lobe of the pituitary to release adrenocorticotropic hormone
(ACTH)
CRH is also synthesized by the placenta and seems to determine
the duration of pregnancy.
Description of the mechanism.It may also play a role in
keeping the T cells of the mother from mounting an immune
attack against the fetus.
• Somatostatin
Somatostatin is a mixture of two peptides, one of 14 amino
acids, the other of 28.
Somatostatin acts on the anterior lobe of the pituitary
to
• inhibit the release of growth hormone (GH)
• inhibit the release of thyroid-stimulating hormone
(TSH)
• Dopamine
Dopamine is a derivative of the amino acid tyrosine. Its
principal function in the hypothalamus is to inhibit the
release of prolactin (PRL) from the anterior lobe of the
pituitary.
• Antidiuretic
hormone (ADH) and Oxytocin
These peptides are released from the posterior lobe of the
pituitary and are described in the page devoted to the pituitary.
27 October 2003.
Ref: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/H/Hypothalamus.html
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