Pituitary gland Flashcards
What is a hormone and how are they transported?
A messenger that is carried from the organ where they are produced to the organ which they affect through the blood stream
How are peptide hormones synthesised?
Synthesised as prohormones requiring further processing (e.g. cleavage) to activate
Where are peptide hormones stored?
Stored in vesicles and then released in response to a stimulus (regulatory secretion)
What receptors do peptide hormones bind to?
Bind receptors on cell membrane and transduce signal using 2nd messenger systems
How are steroid hormones synthesised?
Synthesised in a series of reactions from cholesterol
Where are steroid hormones stored?
They’re not- they’re released immediately (constitutive secretion)
What receptors do steroid hormones bind to?
Bind to intracellular receptors to change gene expression directly
What do hypothalamic parvocellular neurons regulate?
The function of the anterior pituitary
Are hypothalamic parvocellular neurons long or short?
Short
Where do hypothalamic parvocellular neurons terminate?
Median eminence
What factors do hypothalamic parvocellular neurons release and where?
hypothalamic releasing/inhibitory factors (hypothalamic regulatory factors) into capillary plexus in median eminence
What are hypothalamic regulatory factors carried by and where to?
By portal circulation to anterior pituitary
What endocrine cells are in the anterior pituitary?
Somatotrophs
Lactotrophs
Corticotrophs
Thyrotrophs
Gonadotrophs
What is the anterior pituitary regulated by?
hypothalamic releasing/inhibiting factors via hypothalamic-pituitary portal system
Describe the process of the hypothalamic-pituitary portal system
- Axon terminals of hypothalamic neurosecretory cells release hormones (RHs and IHs) into the
hypothalamo-pituitary portal system - The RHs and IHs travel in the portal system to the anterior pituitary
- The RHs and IHs stimulate or inhibit the release of hormones (black dots) from anterior pituitary cells
- Anterior pituitary hormones leave the gland via the blood
What hormone do somatotrophs release?
Growth Hormone (GH)
What hormone do lactotrophs release?
Prolactin
What hormone do thyrotrophs release?
Thyroid stimulating hormone (TSH)
What hormone do gonadotrophs release?
Luteinising hormone (LH)
Follicule-stimulating hormone (FSH)
What hormone do corticotrophs release?
Adrenocorticotrophic hormone
(ACTH)
What are the releasing and inhibiting hormones for growth hormone?
R- GHRH
I- somatostatin
What is the inhibiting hormone for prolactin?
Dopamine
What is the releasing hormone for TSH?
Thyrotrophin releasing hormone
What is the releasing hormone for LH and FSH?
Gonadotrophin releasing hormone
What is the releasing hormone for ACTH?
Corticotrophin releasing hormone
What is the target for growth hormone?
General body tissues (particularly liver)
What is the target for prolactin?
Breasts (in lactating women)
What is the target for TSH?
Thyroid
What is the target for gonadotrophins?
Testes/ovaries
What is the target for ACTH?
Adrenal Cortex
What causes bitemporal hemianopia?
Pituitary tumour pressing on optic chiasma
What are the symptoms of bitemporal hemianopia?
Loss of peripheral vision
What should you ask a patient to assess for peripheral vision decrease
Have you been bumping into things?
What condition happens when children have excess GH?
Gigantism
What condition happens when adults have excess GH?
Acromegaly
Why do adults develop acromegaly and not gigantism?
Because their growth plates are fused so they cannot grow taller
What are the symptoms of acromegaly?
Coarsening of facial features
Macroglossia
Prominent nose
Large jaw - prognathism
Increased hand and feet size
Sweatiness
Headache
What are the posterior pituitary hormones?
- Arginine vasopressin (AVP) (Anti-diuretic hormone)
- Oxytocin
What is the main physiological action of ADH?
stimulation of water reabsorption in the renal collecting duct
What receptors does ADH work with?
V2 receptors- for urine
V1 receptors- for vasoconstriction
What hormone does ADH stimulate the release of?
Stimulates ACTH release from anterior pituitary
Describe the role of the anterior pituitary in lactation
Mechanical stimulation of nipple & surrounding area activates afferent pathways
Afferent signals integrated in the hypothalamus and inhibit dopamine release from dopaminergic neurons
Less dopamine in the hypothalamic-pituitary portal system causes less inhibition of anterior pituitary lactotrophs
Increased plasma prolactin increases milk secretion in mammary glands
Describe the role of the posterior pituitary in lactation
Mechanical stimulation of nipple & surrounding area activates afferent pathways
Afferent signals integrated in the hypothalamus and stimulate oxytocin-releasing neuron activity
Action potentials travel down oxytocin neurons and oxytocin is secreted into the bloodstream
Increased plasma oxytocin increases milk ejection in mammary glands
