Pituitary Gland Flashcards
(27 cards)
Location
Bottom of the brain
covered by Sella Turcica (turkish saddle)
Anterior+Posterior
Connected to hypothalamus.
Why can a pituitary adenoma affect the vision of a patient?
Pituitary is adjacent to the optic nerve, so any growth can compress it and affect vision
Anterior Pituitary
Controlled by peptide hormones released by hypothalamus
Controls the release of hormones that control growth, metabolism, reproduction, stress response, lactation.
Releases hormones into hypophyseal portal veins.
The 6 Hormones of the anterior pituitary gland
ACTH: Adrenocorticotropic hormone, activates cortisol production
FSH-Follicle stimulating hormone, Sperm and Ovary egg release+ estrogen release
LH-Luteinizing Hormone, progesterone (female), Testosterone (male)
HGH- Human Growth Hormone, Height in children, muscles, bones, body fat distribution in adults
Prolactin- Breast milk production after birth
TSH-Thyroid stimulating hormone.
Posterior Pituitary
Enervated by neurones from hypothalamus.
Releases ADH (Vasopressin) (Osmolarity) and Oxytocin (physical stress)
Thyroid Axis
Negative feedback system: too much T3 and 4, decreased TSH.
Thyrotropin-releasing hormone (from Hypothalamus)—-> TSH (anterior pituitary)—–> thyroid gland—–> Thyroid hormones T3 and 4
What are the effects of T3 and 4
growth and development, increased catecholamine effect
Example of catecholamines
Epinephrine, Dopamine, Norepinephrine
Gonadotrophin
Needed for secondary sex characteristics
Intermittent release needed to work
Growth Hormones
Somatostatin inhibits this
Fluctuates, needs dynamic testing
failure of this axis causes acromegaly and dwarfism
Pituitary Adenoma
1 in 4 have them in post mortem findings
1st most common: non functional, 2nd prolactin, 3rd growth hormone.
micro versus macro adenomas.
Macro more than 10mm causes vision problems.
Growth Hormone Adenoma
Causes acromegaly:
Overgrown jaw, big hands, shoe size increases, excess sweating
Risk of colon cancer and other cancer risk increased.
Diabetes mellitus
identified by suppression test
Prolactin adenoma
male secretion of milk from breasts.
Presents earlier in men
CAn be bigger problem in women.
Treatment for an adenoma
Hypophysectomy hole through nose.
Hypothalamic-pituitary- adrenal axis
Corticotropin releasing hormone (from hypothalamus)—-> Anterior pituitary produces ACTH—-> Adrenal gland—-> production of cortisol (and adrenal androgens).
Stress affects this (physical and mental)
ESSENTIAL for life
Release of ACH
spliced from common precursor mRNA (melanocytes gene)
proopiomelanocortin
Excess causes hyperpigmentation (tanned look)
Prolactin
Not part of traditional endocrine axis
Dopamine inhibits release of prolactin by anterior.
Negative regulation
end target breast tissue
Excess prolactin caused by adenoma or damage to pituitary stalk
treatment involves dopamine agonist
If blood flow from the hypothalamus to the pituitary is interrupted, which hormone will NOT be affected?
a) ACH
b) TSH
c)LH
d) ADH
e) growth hormone
d) ADH, because adh is produced by the posterior pituitary gland that is enervated (does not have own venous system) ust neurosecretory cells
Embryonic origins of posterior (neurohypophysis) and Anterior (adenohypophysis)
Anterior: Oral ectoderm, rathke’s pouch invagination
Posterior: Neural ectoderm , Infundibulum
Steps to release hormones from posterior
Synthesis of oxytocin and ADH in hormone secreting nerve cell—–> transport along hypothalmic-pituitary tract to posterior pituitary——> Storage in axon terminals (vesicles)—-> release when hypothalmic neurons fire.
ADH ( Vasopressin, antidiuretic hormone)
9 amino acids with two cysteines attached to eachother
ADH receptors are G protein coupled ones.
V1 receptors: Smooth Muscle
V2: Nephrons (enhances water reabsorption)
Effects of plasma osmolality outside of normal range
- 275-295 mosm/kg
low osmolality causes oedema
-> Brain oedema, brain absorbs water, trapped in limited space, pressure builds up.
Intercranial compartment shift, brain lobes move, damage
High osmolality causes brain shrinkage, water loss
= VERY BAD!!!!
Increased ADH: Increased thirst
What happens when Plasma osmolality is too low?(step by step)
osmotic sensors in brain—-> Hypothalamus (supraoptic nucleus)—–> posterior pituitary—–> ADH—-> Nephrons (aquaphorin insertion causes water reabsorption)
—-> correct osmolality
What is a disease associated with damaged ADH receptors/low ADH secretin?
Diabetes Insipidus
Rare.
Causes polyuria (urinary loss of water)
Polydipsia (thirst)
