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Unformatted text preview: te TSH
4. TSH continues to stimulate
thyroid to overg row.
5. Overgrown thyroid forms a
goiter. Pars Intermedia
In most vertebrates, a portion of the
pituitary anterior lobe adjacent to
the posterior lobe develops into an
intermediate lobe .
ß Principle activity is secreting
melanocyte -stimulating hormone
ß MSH promotes
increased melanin production in
melanocytes in skin and hair.
• Cryptic coloration
• Sexual/ territorial advertising P
I A Pars Intermedia
Alternate processing of the same pro-hormone polypeptide:
Pro- opiomelanocortin (POMC)
[pro- opioid -melanotropin -corticotropin ]
• In anterior pituitary , POMC cleaved to form
endorphins ( opioids ) + adrenocorticotrophic hormone (ACTH)
• In intermediate lobe , ACTH fragment is further cleaved to form
• In humans, intermediate lobe is greatly reduced, but present.
Syndromes that cause an overproduction of ACTH (pregnancy,
adrenal insufficiency [ Addisons disease]) also result in elevated
MSH and hyperpigmentation .
• Red-headed, poorly tanning people often have normal MSH
levels, but decreased MSH-receptors. Heyer Endocrine Pathologies
I. Abnormal hormone titer —
• Primary pathology: caused the endocrine gland secreting that hormone
• Secondary pathology: caused by a factor (e.g., trophic hormone)
regulating that gland
– Hypersecretion of hormone
• Idiopathic: gland “turned on ” for no obvious reason
• Tumor hyperplasia of secretory cells
• Secondary: hypersecretion of trophic hormone
– Hyposecretion of hormone
• Enzyme defect in biosynthesis of the hormone
• Autoimmune destruction of of secretory cells
• Receptor defect/insufficiency responding to trophic hormone
• Secondary: hyposecretion of trophic hormone
II. Abnormal hormone response —
• Number of receptors in target organ: desensitization
• Mutant defective receptors in target organ
• Defective transduction pathway step
III. Exogenous hormones 9...
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This note was uploaded on 09/02/2011 for the course BIOL 6a taught by Professor Staff during the Fall '10 term at DeAnza College.
- Fall '10