Pituitary Gland Flashcards
What synthesizes vasopressin and oxytocin?
PVN (paraventricular nucleus)
SON (supraoptic nucleus)
What does vasopressin do?
Enhance water retention of the kidney via aquaporin water channels
Direct pressor effect via constraction of the smooth muscle in vascular system
Whar are the parts of the vasopressin gene?
- SP
- VP
- NPII
- Copeptin
What is copeptin?
related to vasopressin. Vasopressin is bound to receptors on platelets (extends half life)
Can assay for vasopressin levels
What are the vasopressin receptor in the kidneys?
AVPR2
What is the receptors for vasopressin in vascular system?
AVPR1a
What kind of hormone is vasopressin?
Peptide (9 aa with disulfide bond)
What provides feedback regulation to the vasopressin effect?
Volume and pressor receptors
to see pressor effect, must mask the baroreceptors
How is vasopressin released?
Made in hypothalamic MNC, Packaged into vesicle and sent to posterior pituitary where it is stored. It is released when stimuli acts on hypothalamus and calcium influx
What causes the release of vasopressin?
- High plasma osmolality (MNC in hypothalamus)
- Low blood volume or pressure (IX and X)
- increase plasma angiotensin II (SFO)
What hormone has a permissive effect on vasopressin?
Aldosterone
What is the ultimate result from increased vasopressin?
Anti-diuresis (concentrated urine)
What counteracts vasopressin and aldosterone?
Atrial natriuretic peptide
What is the action of increased vasopressin?
Increase permeability to water -aquaporin insertion -Water flow out of tubule/duct in kidney Increase thirst Smooth muscle contraction
What happens when MNCs sense high osmolality?
Increase action potentials to release more vasopressin
What is the stimulus of the regulation of vasopressin?
- Osmotic difference
- Hypovolemia
- blood pressure in jeopardy
What are the receptors involved in the regulation of Vasopressin?
- NTS
- SFO
What are compensatory reaction from vasopressin signaling?
Salt and water intake
What is a disease that relates to loss of vasopressin?
Diabetes insipidus
What are the signs of diabetes insipidus?
Polyuria, polydipsia, urine of low specific gravity, dehydration
What does pathognomic mean?
A sign specifically characteristic of a particular disease
What are some causes of diabetes insipidus?
- Central DI
- Nephrogenic DI
- Psychosomatic polydipsea
- Inappropriate ADH secretion
How can you rule out central DI?
Determine whether endogenous ADH can occur and if it is increased and so does concentration of urine it is not central DI
How can you rule out nephrogenic DI?
If there is a response to exogenous ADH it is not nephrogenic
How can you treat hypothalamic DI?
- Nothing if it is getting adequate water
- Exogenous ADH
What could cause inappropriate ADH secretion?
Release ADH with no osmotic or volume stimulation. Usually from neoplastic processes
How can you treat nephrogenic DI?
- Thiazide diuretics
- Chlorothiazide
- Hydrochlorothiazide
- Dietary potassium
What does Oxytocin stimulate?
- Contraction of myometrium
- Milk letdown reflex
What is different about the regulation of oxytocin?
Positive or open loop regulation
What stimulates Oxytocin release?
Sight, smell, sounds, or nursing of young
What is the events of milk letdown?
Oxytocin causes secretory alveoli to contract-> milk flows into intralobular duct->goes into lobular duct-> gland cistern-> teat cistern-> teat canal-> milk ejected
Describe the positive feedback loop of oxytocin?
Mechanical stimulation of cervix-> oxytocin release-> relaxes cervix and contracts uterus-> more oxytocin
What are the different oxytocin effects?
- Glucocorticoid receptor: reduce cortisol
- Alpha 2 receptor: blocks norepinephrine stress effects
- Opiodergic activity: Reward and pain free
- 5-HT synthesis: happiness
- Cholinergic activity: Calm and sleep
Describe the oxytocin receptors.
There is only one receptor but there are different polymorphisms that can give it different functions
What are the four main hypophysiotrophins of the anterior pituitary?
- Growth hormone (GH)
- Somatostatin (GHIH)
- Corticotropin (ACTH)
- Thyroid-stimulating hormone (TSH)
How are anterior pituitary hormones controlled?
Releasing factors that are made in the hypothalamus and released at the median eminence into portal blood and then acts on the anterior pituitary
What is the TRH?
Thyrotropin releasing hormone. Half life is 2-6 min.
What are the effects of TRH?
Release of TRH into portal system and causes thyrotropes to produce TSH from the thyroid and then T3 and T4 are secreted
Do TRH and TSH impact calcitonin
No
What hormones does TRH effect?
GH, ADH, Prolactin, cortisol (horses)
What is CRH?
Corticotropin releasing hormone. 41 AA peptide. Secreted by median eminiece and PVN neurons
What are the effects of CRH?
Released into portal system and stimulates the release of ACTH
What is POMC?
Pro-opiomelanocortin.
What is the N terminal of POMC?
Produces a strong proliferation in adrenal cortex as well as ACTH
What is the Prohormone Convertase I?
Made in pars intermedia and cleaves the POMC and makes alpha MSH and ACTH
What is GH?
Growth hormone. Polypeptide 191 AA. Made in somatotrophs in response to GHRH
What are some effects of GH?
Production if IGFs in the liver, muscle, and bone. Lipolytic effect
What are somatomedins?
IGFs that mediate GH effects. Provides feedback to shut off GH and stimulate GHIH
What increases GH release?
- Sleep
- Hypoglycemia
- incr Plasma aa (Arg)
- Ghrelin (hunger stimulating peptide hormone from the stomach)
- Exercise
What decreases GH release?
- Hyperglycemia
- Glucocorticoids
- Somatomedins
- Somatostatin
Which hormone has the lowest species homology?
Growth hormone
What is Homeorhesis
Shift in metabolism associated with lactation
What is the effects of GH on bones?
- Promote chondrogenesis in epiphyseal plate
- Promote production of bone matrix
What is the metabolic effect of GH?
- Promotes aa uptake (per insulin)
- Promotes lipolysis in adipocytes
- Improve nutrient utilization
- Diary cows: increase milk production
What is Pituitary Dwarfism?
Fairly rare. Deficiency of GH. Seen in dogs most common in German Sheperd’s. Due to a cystic Rathke’s pouch
What are some clinical signs of young animals with pituitary dwarfism?
- Proportional dwarfism
- Delayed dentition
- Delayed closure of growth plates
- Haircoat abnormalities
- Reduced exercise performance
What is the clinical signs of adults with pituitary dwarfism?
- Abnormal weight gain
- Reduced lean mass
- Reduced exercise performance
- Osteopenia
What are some diagnosis of pituitary dwarfism?
-Insulin growth factor
-Relaxation
-Sedation
Should see increase of GH with these
What is acromegaly?
Hypersomatotropism. Excess GH post puberty. Rare in dogs
and sometimes seen in older male cats. Get growth of membranous bones
What are some causes of acromegaly?
- Pituitary adenomas
- Pituitary hyperplasia
What are signs of acromegaly?
- Weight gain
- Lean body in animals with diabetes mellitus
- Enlarged jaw, tongue, forehead and extremities
- Failure to shed
How can you diagnose acromegaly?
Glucose suppression test
What does the intermediate lobe produce?
alpha-MSH
POMC convertase 1
POMC convertase 2
What regulates the pars intermedia?
regulated by dopamine which inhibits release
What can cause and PPID parkinson’s?
Dopamine insufficiency
What is PPID?
Pituitary pars intermedia disfunction. Looks like Cushing’s disease but it is from a loss of dopamine
