Quiz 3 Endocrine Flashcards
Hormones
Blood-borne chemical messengers that affect target cells anatomically distant from the secreting cell
- Regulates: Growth and development
- Metabolism
- Sexual function
- Reproduction
- Mood stability
Hormones are classified by
Action - the effect they have (insulin lowers glucose)
Source - Anterior or posterior pituitary
Chemical structure
Hormones are categorized by chemical composition
Steroids - androgens glucocorticoids, thyroid (lipids)
Proteins/polypeptides - Insulin, growth hormone (water)
Amines/amino acids - epinephrine (water)
Fatty acid derivatives - prostaglandins
Water soluble hormones
Bind to cell surface receptors
Peptides (small proteins) majority of endocrine hormones
Easily transported in the bloodstream
ACTH FSH LH, Growth Hormone, TSH PTH
Lipid Soluble Hormones
Carried in circulation by transport proteins (globulin) poorly soluble
Activate intracellular receptors
Thyroid hormones (T3, T4) with iodine attached
Steroids - derived from cholesterol
Hormone detaches at the site of the target cell
Mechanism of Water Hormones with Cell Membrane Receptors
Hormones exert their action by binding to target cell receptor proteins
Water-soluble hormones have a hormone-binding site located on the external portion of a specific cell surface receptor
Once binding takes place, receptor protein conveys a signal to the interior of the cell to produce a response
Amplification of Hormone Activity
Why you can have a very small amount of circulating protein and it can cause a tremendous effect on the body.
Progressively larger numbers of chemical reactions occur at each step, resulting in the activation of numerous G proteins
Mechanisms of Lipid Hormone Action
Steroid (lipid) hormones diffuse easily through the lipid bilayer of the cell membrane; cell membrane carriers transport thyroid hormones
Thyroid and steroid receptors located in the cytoplasm or in the nucleus of the target cell
Once inside the cell lipid hormones have to go through gene expression to have the effect amplified.
Lipid acts slower than water-soluble bc of the multiple steps and gene expression that has to take place before amplification can take place.
Hormone Synthesis - Water soluble
Peptide hormones are contained within the bilayer of the vesicles and stored until a trigger results in the exocytosis of the hormone into the extracellular space
Hormone Synthesis - Lipid Soluble
Steroid (Lipid) Hormones are formed on-demand from cholesterol that is stored in the cell or retrieved from the circulating lipoproteins.
Hormone Synthesis - Thyroid Hormone
Thyroid hormones (lipid-soluble) are formed on demand but are trapped attached to thyroglobulin and sit and wait until they are told its time to be released by the hypothalamus or anterior pituitary
Factors affecting hormone secretions
Feeding-fasting cycle
Light dark cycle
Sleep-wake cycle
24 hour (circadian cycle)
Longer cycles (28-day menstrual cycle)
Anterior pituitary gland hormones are regulated
by the hypothalamus
When do you measure cortisol for testing
First thing in the morning when its at the highest
Explain Negative feedback control
The body says it need so much of a hormone the body reacts to it and it sends a signal back to the anterior pituitary and hypothalamus that fx at a good level.
If we don’t need as much hormones it will send a message back that to the anterior pituitary to slow down production
If deficient in hormone sends signal to anterior pituitary and hypothalamus that we need more
How we keep hormone level fx and at level we want
Hormone Metabolism/Excretion
Water Soluble
vs
Lipid Soluble
Water-soluble hormones - Finds their way out in urine
Lipid- soluble hormones are bound to plasma proteins and stored in adipose tissue so they remain in circulation for longer periods of time
Metabolized by kidney and liver; degraded by target cell after binding to receptors
Half life of a hormone
Duration of hormone activity in circulation expressed in minutes, hours, or days
its the time for a hormone to reach one half of its original concentration in the blood and is influenced by the rate uptake by cells, degradation, and excretion
Lipids usually have a longer half life
Heavier people with more adipose tissue may hold onto hormones a lot longer than someone with no adipose tissue
Pharmacologic Hormone Concentrations
vs
Physiologic hormone concentrations
Physiologic hormones are extremely low due to amplification
Pharmacologic levels are much higher
Tissue response to pharmacologic hormone concentrations may be significantly different from physiologic levels
Regulation of Receptor Responses
What determines the ability of a cell to respond to a particular hormone
Cell response to a hormone depends on the presence of specific receptors on very specific cells
for that hormone on the cell called the target cells
A cell can change how it wants to respond to a hormone by changing the # of receptors or an affinity for the hormones
Affinity
The degree of “tightness” or the hormone receptor bond or the inclination of the hormone to remain bound to the receptor
i.e. Old key locks you put key in a jiggle it around present-day locks have a high affinity with tight locks only fitting the intended key
When you have a high affinity you don’t need as much of the hormone you can use a very small amount
Specificity
The “fit” of a hormone into a receptor binding pocket
Cross specificity
One receptor site will respond to two or more different hormones.
May occur between hormones
Example is growth hormone and prolactin both can bind to a prolactin receptor so if growth hormone take up all the receptors their won’t be any for prolactin
Down regulation
Cells have been exposed to a high concentration of a hormone so the body to protect itself decreased the # of receptor sites available, so it doesn’t have excessive activity
example: insulin receptors
Chronic high glucose levels so the body is putting out a lot of insulin trying to fix the level so the body shuts down insulin receptor cells. This is how insulin resistance occurs
