How can we help?

You can also find more resources in our Help Center.

68 terms

Endocrinology

Fundamental Module
STUDY
PLAY
What is a hormone?
A chemical that acts as an interceullar communicator.
What is a neural hormone?
Neurotransmitter (acts locally)
How does a endocrine hormone work?
Reaches systemic circulation and influences cells some distance away
What is the definition of a neuroendocrine hormone?
-secreted from neurons and travel through the blood stream
- influence cells some distance away
What is an example of a neuroendocrine hormone?
- ADH
- Epinephrine
What are steroids derived from?
Cholesterol
What are 3 derivatives of the amino acid tyrosine?
- Epi
- Norepi
- Thyroxine
Explain the control of hormones through a negative feedback loop.
- Increased functioning of target cells results in a decreased rate of hormone from original secreting cell
What is an example of a positive feedback loop?
Dilation of the cervix in labor stimulates the posterior pituitary to secrete oxytocin which causes further dilation of cervix
How do steroid hormones act on cells?
- Enter the cell and bind to intracellular receptors to activate genes
- Activating gene causes transcription and translation of proteins
Which has a quicker effect as a hormone treating poison oak Epi or prednisone?
- Epi is fast
- Prednisone is a hormone which is slow acting
What is a problem with measuring hormones?
- If there is only a small quantity available it is hard to measure
What test would you run to look at hormones?
- Typically a radioimmunoassay
Do lab test measure the biological activity of a hormone??
- No they only measure the amount of hormone
What are the two tissue types of the pituitary gland?
- Adenohypohysis (anterior)
- Neurophypophysis (posterior)
What controls pituitary secretions?
Hypothalamus
What does the posterior pituitary secrete?
- ADH
- Oxytocin
Where are the cell bodies which produce ADH and oxytocin located?
-Supra optic nuclei of hypothalamus
-Paraventricular nuclei of hypothalamus
How are neuropeptides from the posterior pituitary secreted?
- Directly from neuron into systemic circulation
What are the 6 hormones of the anterior pituitary?
- FSH
- TSH
- GH
- ACTH
- LH
- Prolactin
What controls the release of the 6 hormones in the anterior pituitary?
- Releasing hormones from the hypothalamus
How is the anterior pituitary and hypothalamus connected?
-Hypothalamic-hypophysial portal blood vessels
What neurotransmitter inhibits the release of prolactin?
Dopamine
What does ADH do?
- Regulates osmolarity of the body by altering renal excretion of water
- Acts on principle cells of distal renal tubules and collecting ducts to increase H20 re-absorption
What causes the release of ADH from the anterior pituitary?
- osmoreceptors in the hypothalamus are sensitive to blood osmolarity
- baroreceptors in the left atrium, aortic arch, carotid artery sense hypo/hyper volemia which signals the hypothalamus via the vagus nerve to decrease or increase secreation of ADH
What stimulants can cause ADH release?
- Pain
- Nausea
- Hypoglycemia
- Certain drugs
What inhibits ADH?
- Alcohol
- ANP
What is SIADH?
- stands for syndrome of inappropriate ADH secretion
- a decrease in plasma osmolarity
- total body sodium is normal, too much total body free water
What is SIADH associated with?
- Oat cell carcinoma of the lung
- The oat cell will secrete ADH
What is the main action of Oxytocin?
- Uterine contractions
- "Let down of milk"
- Milk ejection
What stimulates the release of oxytocin?
- Suckling or nipple stimulation
- sight, sound, smell of infant
- Cervical dilation during labor and orgasm
How is oxytocin used clinically?
- Induce labor
- Reduce postpartum bleeding
- Psychiatric treatment
What are the 5 cell types that make the 6 anterior pituitary hormones?
- Thyrotroph
- Corticotroph
- Lactotroph
- Somatotroph
- Gonadotroph
When is the largest pulsatile release of GH?
- First hour of falling asleep
What is the action of GH?
- Increase linear grown pre-closure of ephysial plate
- Increase protein synthesis
- Increase lean body mass
- Utilization of fats for energy source
- Increases insulin resistance (diabetogenic)
What stimulates the release of GH?
- Fasting
- Starvation
- Increased plasma levels of amino acids
- Exercise
What is acromegaly?
- Excessive GH in adults
What is gigantism?
- Excessive GH in children/teens
What happens if you are deficient in GH?
- Failure to grow
- Short stature
- Mild obesity
What inhibits Prolactin from being released on a constant basis?
- Dopamine
What is lactogenesis?
- Stimulation of milk production and secretion in response to suckling
What does Prolactin do?
- Lactogenesis
- Inhibits GnRH which inhibits ovulation
- Breast development at puberty and pregnancy
What does too much prolactin cause?
- Galactorrhea
- Infertility in males secondary to impaired spermatogenesis
What is galactorrhea?
- Too much prolactin causes destruction of dopamine source
- Hypothalamic-hypophysial portal tract interruption from pituitary tumor or trauma
How do you treat galactorrhea?
-Dopamine agonist (bromocriptine)
-
What happens if you are deficient in Prolactin?
- Failure to lactate
- Empty sella syndrome
What is a headache and galactorrhea a presenting symptom of?
Pituitary adenoma (30% of cases hyperprolactinemia)
What are the actions of TSH?
- Regulation of thyroid gland
- Regulates secretion of thyroid hormones, T3 & T4
What hormone provides the negative feedback for a steady state of secreted thyroid hormone?
T3
What percent of thyroid hormone is protein bound?
99%
Which is more physiologically more active T3 or T4?
T3
When do you have the highest levels of ACTH?
In the morning
What is ACTH derived from?
Pro-opiomelannocortin
What does the ACTH "family" include?
- ACTH
- MSH (melanocyte stimulating hormone)
- Beta
- Alpha & beta lipotropin
What is the main action of ACTH?
Modulate cortisol secretion from the zona fasciculate of the adrenal cortex
What controls the release of ACTH?
Corticotrophin- releasing hormone
What controls the release of FSH?
Gonadotropin releasing hormone
What is the action of FSH?
- Stimulate development of follicles in ovary
- Stimulate spermatogenesis
What controls the release of LH?
Gonadotropoin- releasing hormone
What does LH do?
- Stimulates development of corpus luteum in ovaries
- Stimulates testosterone secretion of Leydig cells in testis
What effect does estrogen and progesterone have the hypothalamus?
Influence the release of FSH and LH
Where is T4 converted to T3?
Target tissue
What do thyroid follicles contain?
Thyroglobulin which contains thyroid hormone
What concentration is iodide in the thyroid compared to outside?
30 X greater than in blood
What is the half life of T4?
7 days
What is the half life of T3?
1 day
How does thyroid hormone work?
- Intracellular hormone that binds to DNA
- Increases transcription
What does thyroid hormone do?
- Increases cellular metabolic rate