AVP, oxytocin, growth hormones and pituitary Flashcards
What is the pituitary gland?
Integrates signals and releases hormones that regulate the functions of other endocrine glands.
Vital roles in homeostasis
What is the two lobes the pituitary gland split into?
Anterior and posterior
What is the driving force of the pituitary gland?
The hypothalamus
Where is the pituitary gland located?
Base of the brain attached to the hypothalamus
Anterior lobe of the pituitary gland
Synthesizes and secretes hormones in response to hypothalamic regulation.
Posterior lobe of the pituitary gland
Stores and secrets hormones synthesized in the hypothalamus. (Does not produce any hormones)
Does the posterior pituitary produce hormones?
No
What two hormones are stored secreted by the posterior pituitary?
Antidiuretic hormones (ADH/vasopressin) Oxytocin
What does antidiuretic hormone regulate (ADH/vasopressin)?
Regulation of renal failure
What does oxytocin regulate?
Regulation of uterine contraction
What the 4 things that feed into the hypothalamus that stimulate the posterior pituitary gland?
- Hyperosmolarioty (main)
- Angiotensin II (main)
- Decreased atrial receptor firing
- Sympathritric stimulation
What two reports does ADH/vasopressin work on?
V1 and V2
What does activation of the V1 receptor do?
Acts on the blood vessels casing constriction, increased systemic vascular resistance.
What does activation of the V2 receptor do?
Kidneys, fluid reabsorption, increased blood volume
What is the overall affect of vasopressin/ADH after activation V1 and V2?
Increased arterial pressure (increased BP). V2 regulates water excretion by decreasing, so retaining water.
Effect of reduced ADH/vasopressin
Diabetes insipidus, copious hypotonic urine.
Treatment for reduced ADH/vasopressin
V2 agonist - desmopressin (mimics vasopressin)
Effect of excess ADH/vasopressin
Hyponatremia (diluted NA due to excess water)
Oedema
Treatment for excess ADH/vasopressin
Demeclocycline (blocks transduction of V2)
Tolvaptan (V2 antagonist) (expensive)
Restrict fluids
Cause of excess ADH/vasopressin
Tumor, head injury, TB
ADH/vasopressin mechanism (5)
- Hypothamalus stimulates posterior pituitary through hyperosmolarity and angiotensin, II
- Vapsoresisibe secreted and acts of V1 and V2 receptor.
- V1= blood vessel constriction = increased systemic vascular resistance
- V2= Kidney fluid reapportion = increased blood volume (water retention)
- Increased arterial pressure
Oxytocin mechanism (3)
- Stretch of uterus, uterine cervix and stimulation of breasts increases action potentials in axons of oxytocin-secreting neuron.
- Action potential go to hypothalamus and simulation secretion of oxytocin via posterior pituitary
- Oxytocin release increased uterine contraction and milk release from breasts.
Clinical use of oxytocin (3)
Labour induction (Slow IV)
Prevention/treatment of hemorrhage (Prophylactic IM)
Labour too quick (Antagonist: Atosiban)
Two types of hormones produced and secrete by anterior pituitary
Tropic and directly acting
What do tropic pituitary hormones do?
Affect the section of other endocrine glands
What do directly pituitary hormones do?
Act directly on pituitary glands
Tropic pituitary hormones (3)
- Adrenocorticoid hormones (corticotrophin)
- Follicle-stimulating hormone (FSH) and luteinising hormone (LH)
- Thyrotropin (Thyroid stimulating hormone
Directly pituitary hormones (2)
Growth hormone (somatropin) Prolactin
Adrenocorticotropic hormone
(corticotropin) target
Adrenal glands
Follicle-stimulating hormone (FSH) and luteinising hormone (LH) target
Reproductive system
Thyrotropin (thyroid-stimulating
hormone) target
Thyroid gland
Growth hormone (somatotropin) target
Liver, bone, muscles
Prolactin target
Mammary glands
Adrenocorticotropic hormone
(corticotropin) effect
Stimulate production of glucocorticoids, which regulate metabolism and stress response
Follicle-stimulating hormone (FSH) and luteinising hormone (LH) effect
FSH stimulates maturation/production of sex cells LH stimulates sex hormones by the gonads
Thyrotropin (thyroid-stimulating
hormone) effect
Stimulates the release of thyroid hormones which regulate metabolism
Growth hormone (somatotropin) effect
Induce production of insulin-like growth factors, which stimulate body growth and higher metabolic rate
Prolactin effect
Promotes milk production
Adrenocorticotropic hormone
(corticotropin) RH/IH
Corticotropin-RH
Follicle-stimulating hormone (FSH) and luteinising hormone (LH) RH/IH
Gonadotropic RH
Thyrotropin (thyroid-stimulating
hormone) RH/IH
Thyrotropin-RH
Growth hormone (somatotropin) RH/IH
Growth hormone-RH and Growth
hormone-IH (somatostatin)
Prolactin RH/IH
Prolactin-RH and prolactin-IH
(dopamine)
What are hypothalamic releasing factors?
Peptides
Some regulate more than one hormone, and some hormones regulated by more than one releasing factor
They also can on neurotransmitters in the CNS.
Anterior pituitary hormone regulation mechanism general
- Hypothalamus detects need for inhibition or increase of hormones and relapses RH/IH.
- IH turns pituitary off
- RH stimulates pituitary release of hormone to act on tissue which has an effect.
- After desired effect, feedback to hypothalamus and pituitary to stop.
When are high levels of growth hormone released? (4)
- Exercise
- Sleep
- Stress
- Thyroid hormone enhanced secretion
What is the growth hormone sensitive to?
Very sensitive to noradrenergic activation, beta-antagonist promotes secretion and alpha antagonist inhibit secretion.
Two types of growth hormone deficiency
Secretion deficiency
Receptor defects
Growth hormone secretion deficiency effects
Hypothalamic or pituitary dysfunction e.g. turners syndrome
Growth hormone receptor defects effects
Laron type dwarfism; fail to produce IGF in response to GH
Clinical manifestation of growth deficiency dependent on age
Children: growth retardation/dwarfism
Adult: increased body fat, decreased muscle and bone mass
Treatment for dwarfism due to growth hormone section deficiency
Somatropin – SC injection strict guidelines for use and specialist initiation.
What neurotransmitter can reduce growth hormone secretion?
Dopamine
Growth hormone and glucose
Counter-regulates glucose:
Hyperglycemia action
Causes insulin resistance
What neurotransmitter can reduce prolactin release?
Dopamine
Hyperprolactinemia
Too much prolactin
Treatment for hyperprolactinemia: Bromocriptine
Dopamine agonist
Reduces prolactin secretion
Treatment for hyperprolactinemia: Cabergoline
Alternative dopamine agonist
Less side effects
Less data in pregnancy
Treatment for hyperprolactinemia: Quinagolide
Non-ergot alkaloid
