487
CHAPTER THIRTEEN
Endocrine System
Many hormones use
cyclic adenosine monophosphate
(cyclic AMP, or cAMP) as a second messenger. In this
mechanism, a hormone binds to its receptor, and the result-
ing hormone-receptor complex activates a protein called a
may alter the function of enzymes or membrane transport
mechanisms, changing the concentrations of still other cel-
lular components. The hormone that triggers this cascade of
biochemical activity is considered a
f
rst messenger.
The bio-
chemicals in the cell that induce the changes recognized as
responses to the hormone are called
second messengers.
TABLE
13.3
|
Types of Hormones
Type of Compound
Formed from
Examples
Amines
Amino acids
Norepinephrine, epinephrine
Peptides
Amino acids
ADH, OT, TRH, SS, GnRH
Proteins
Amino acids
PTH, GH, PRL
Glycoproteins
Protein and
carbohydrate
FSH, LH, TSH
Steroids
Cholesterol
Estrogens, testosterone,
aldosterone, cortisol
TABLE
13.2
|
Hormone Names and Abbreviations
Source
Name
Abbreviation
Synonym
Hypothalamus
Corticotropin-releasing hormone
CRH
Gonadotropin-releasing hormone
GnRH
Luteinizing hormone releasing hormone (LHRH)
Somatostatin
SS
Growth hormone release-inhibiting hormone (GRIH)
Growth hormone-releasing hormone
GHRH
Prolactin release-inhibiting hormone
PIH
Dopamine
Prolactin-releasing factor*
PRF*
Thyrotropin-releasing hormone
TRH
Anterior pituitary gland
Adrenocorticotropic hormone
ACTH
Corticotropin
Follicle-stimulating hormone
FSH
Follitropin
Growth hormone
GH
Somatotropin (STH)
Luteinizing hormone
LH
Lutropin, interstitial cell-stimulating hormone (ICSH)
Prolactin
PRL
Thyroid-stimulating hormone
TSH
Thyrotropin
Posterior pituitary gland
Antidiuretic hormone
ADH
Vasopressin
Oxytocin
OT
Thyroid gland
Calcitonin
Thyroxine
T
4
Tetraiodothyronine
Triiodothyronine
T
3
Parathyroid gland
Parathyroid hormone
PTH
Parathormone
Adrenal medulla
Epinephrine
EPI
Adrenalin
Norepinephrine
NE
Noradrenalin
Adrenal cortex
Aldosterone
Cortisol
Hydrocortisone
Pancreas
Glucagon
Insulin
Somatostatin
SS
*
”Factor” is used because a speci±
c prolactin-releasing hormone has not yet been identi±
ed.
TABLE
13.4
|
Sequence of Steroid
Hormone Action
1. Endocrine gland secretes steroid hormone.
2. Steroid hormone di²
uses through target cell membrane and enters
cytoplasm or nucleus.
3. Hormone combines with a receptor molecule in the cytoplasm or
nucleus.
4. Steroid hormone-receptor complex binds to DNA and promotes
transcription of messenger RNA.
5. Messenger RNA enters the cytoplasm and directs protein synthesis.
6. Newly synthesized proteins produce hormone’s speci±
c e²
ects.
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