Endocrine Function I: Basic Concepts, Hypothalamic, and Pituitary Hormones Flashcards
Five basic functions of hormones
- Maintenance of consistency of chemical composition of extra and intracellular fluids
- Regulation of growth and development of the body, plus development of male and female sex characteristics
- Promotion of sexual maturation, maintenance of sexual rhythms and facilitation of the reproductive process
- Regulation of energy production; stabilization of the metabolic rate; tight regulation of salt, water, CHO, fat, and protein metabolism
- Helping the body adjust to stress
Three major classes of hormones
- Protein
- Steroid
- Amino acid derivatives
Protein
- Specific chemical composition and derivation
- Example
- Amino acid (water soluble, travels through bloodstream w/o carrier)
- All “P” organs: pituitary, hypothalamus, parathyroid, portions of the GI tract, and pancreas
Protein
- Mechanism of action
These (along with catecholamines or protein-bound hormones), effect their cellular action by binding to cellular receptors. They need a “second messenger” to pass their cellular message to interior of cell.
Why is a second messenger necessary?
The first messenger is the protein polypeptide, or catecholamine hormone itself, because it is not lipid-soluble, it cannot pass through the membrane.
The second messenger is ____ ____, formed by adenyl cyclase catalysis
cyclic AMP (cAMP)
Steroid hormone
- Specific chemical composition and derivation
- Example
- Derived from cholesterol
- Nucleus: Perhydrocyclopentanophenanthrene
Steroid hormone
- They’re hydrophobic and require ____ ____ to be transported in blood. Must dissociate from carrier to be biologically active; the ____ hormone is biologically active
Carrier proteins; FREE
Steroid hormone
- Metabolism
- They must be catabolized by liver to water-soluble, inactive forms
- Hydroxylation, oxidation, or reaction w/ glucuronic acid or sulfate forms conjugates, which are excreted in the urine
Steroid hormone
- Mechanism of action
Lipid-soluble so pass through cell membrane, then they associate with a specific cytoplasmic receptor protein. This is transported to cell nucleus, inducing messenger RNA synthesis
Aromatic amine hormones are small molecules derived from the amino acid ____
Tyrosine
Aromatic amine hormones
- Examples
Includes both thyroid hormones and catecholamines hormones from the adrenal medulla
Aromatic amine hormone
- Are ____-____ and require carrier proteins, principally albumin, for transport in bloodstream
Water-insoluble
Aromatic amine hormone
- Catabolism and excretion
Catabolized in liver by deiodination or oxidation to inactive forms to be excreted
Aromatic amine action
- Thyroid hormones use what pathway to enter the cell?
mRNA pathway
Aromatic amine action
- Catecholamines use what pathway to enter the cell?
Use the second messenger (cAMP) pathway
ESSAY: What is the importance of feedback mechanisms?
W/o feedback, homeostasis is not maintained and person gets “sick”
ESSAY: Explain negative feedback
When you have too much final product, you send signals to the first and second steps to tell them not to produce any more stimuli
ESSAY: Explain positive feedback
Usually in pregnancy, keep producing estrogen: ↑ estrogen → ↑ FSH/LH → ↑ feedback → ↑ estrogen
What does the hypothalamus synthesize from specialized neurosecretory cells?
Neurocrine polypeptide releasing factors
What is the interaction of hypothalamic releasing factors and anterior pituitary hormones?
The hypothalamus can produce releasing AND inhibiting factors that will work on the anterior pituitary to produce more hormones
Anterior pituitary produces either trophic or direct-acting hormones. How do they elicit their effects on the target organ?
- Trophic: stimulate another endocrine gland to manufacture a second hormone that affects metabolism
- Direct acting: elicit effects directly one the target organ
What does the posterior pituitary do?
Stores and releases (does NOT manufacture) hypothalamic hormones
What are the two hormones that posterior pituitary stores?
ADH (vasopressin) and oxytocin
General causes of primary hormonal dysfunctional states
Involves the target organ producing hormone
General causes of secondary hormonal dysfunctional states
Generally involves the trophic hormone produced at the pituitary level
General causes of tertiary hormonal dysfunctional states
Generally involves the releasing factors produced at the hypothalamic level
What is the clinical usefulness of baseline level tests?
Randomly drawn specimen that reveals hyperfunction or hypofunction, but does not reveal the mechanism or level of dysfunction
What is the clinical usefulness of stimulation tests?
Used to assess a HYPOFUNCTIONING endocrine organ; useful in determining the reserve capacity of an endocrine organ to produce hormone
What is the clinical usefulness of suppression test?
Used to assess a HYPERFUNCTIONING endocrine organ; useful in pinpointing the level of dysfunction
Primary hyperpituitarism
- Hormone involved in the most common dysfunction
Prolactin-secreting adenoma
Primary hyperpituitarism
- Time frame in which growth hormone dysfunction causes acromegaly and gigantism
- Gigantism: too much growth before growth plate or long bones seal (childhood)
- Acromegaly: after closure so growth of cartilage areas (later on in life)
Most common cause of secondary hyperpituitarism
Neurogenic tumors of the hypothalamus
Two common causes associated w/ pnhypopituitarism
Hemorrhages and tumors are most common causes
Typical hormone levels associated w/ panhypopituitarism
Onset is gradual with initial loss of GH, LH, and FSH, followed by TSH, ACTH, and finally PRL
Disease state associated w/ a deficiency of antidiuretic hormone (ADH)
Diabetes insipidus
Disease state associated w/ an excess of antidiuretic hormone (ADH)
SIADH
A substance produced by specialized cells in some part of the body and carried by the bloodstream to target organs in the body
Endocrine hormone
A substance synthesized in neurons and released into the extracellular space, binding to receptors in nearby cells to affect function
Neurocrine hormone
A substance synthesized in endocrine cells and released into the intestinal lumen
Exocrine hormone
?
Acromegaly
Trophic hormones produced by the anterior pituitary
- TSH
- ACTH
- FSH
- LH
TSH
- Full name
Thyroid-stimulating hormone
TSH
- Specific target organ(s)
Thyroid gland
TSH
- Principle biological effects
Stimulation of thyroid hormone formation and secretion
TSH
- Chemical nature
Glycoproteins
FSH
- Full name
Follicle-stimulating hormones
FSH
- Specific target organ(s)
Testis or ovary
FSH
- Principle biologic effects
- Men: spermatogenesis and seminiferous tubule development
- Women: follicular growth
FSH
- Chemical nature
Glycoprotein
LH
- Full name
Luteinizing hormone
LH
- Specific target organ(s)
Testis or ovary
LH
- Principle biologic effects
- Men: stimulation of interstitial tissue; androgen secretion
- Women: stimulation of ovulation; corpus luteum formation; progesterone secretion
LH
- Chemical nature
Glycoprotein
ACTH
- Full name
Adrenocorticotrophic hormone
ACTH
- Specific target organ(s)
Adrenal cortex
ACTH
- Principle biologic effects
Adrenocortical hormone biogenesis and release
ACTH
- Chemical nature
Polypeptide
PRL
- Full name
Prolactin
PRL
- Specific target organ(s)
Mammary gland
PRL
- Principle biologic effects
Mammary gland proliferation; initiation of milk secretion, insulin antagonist
PRL
- Chemical nature
Protein
GH
- Full name
Growth hormone (somatotropin)
GH
- Specific target organ(s)
Body as a whole
GH
- Principle biologic effects
Growth of bone and muscle
GH
- Chemical nature
Protein
MSH
- Full name
Melanocyte-stimulating hormone
MSH
- Specific target organ(s)
Skin
MSH
- Principle biologic effects
Dispersion of pigment granules; skin darkening
MSH
- Chemical nature
Peptide
ADH
- Full name
Antidiuretic hormone (vasopressin)
ADH
- Specific target organ(s)
Renal tubules
ADH
- Principle biologic effects
Water reabsorption
ADH
- Chemical nature
Peptide
Oxytocin
- Target organ(s)
Smooth muscles (uterus, mammary gland)
Oxytocin
- Principle biological effects
Contraction, ejection of milk
Oxytocin
- Chemical nature
Peptide
Direct-acting hormones produced by the anterior pituitary
- PRL
- GH
- MSH
