Endocrinology Flashcards
What hormones are secreted by the anterior pituitary?
- TSH
- GH
- LH
- prolactin
- adrenocorticotrophic hormone (ACTH)
- FSH
The release of these hormones is dependent on stimulation from the hypothalamus via the portal vascular system.
What kind of hormone is aldosterone?
Mineralocorticoid
Where is aldosterone synthesised?
Zona glomerulosa of adrenal cortex
What stimulates secretion of aldosterone?
Hyperkalaemia, angiotension II and ACTH
Where does aldosterone act to cause sodium retention?
In the DCT.
It also causes potassium loss here.
What syndromes cause high/low aldosterone levels?
High in Conn’s syndrome.
Low in Addisons’s disease.
How does aldosterone affect cAMP?
Aldosterone acts on intracellular receptors to produce specific gene transcription.
cAMP concentrations are altered due to agonist effects on extracellular 2nd messenger receptors
=> aldosterone does NOT increase intracellular cAMP
Is insulin a positive inotrope?
Yes
Where is insulin secreted from?
Beta cells within Islets of Langerhans
What does insulin do to triglycerides?
Causes triglyceride formation and fat deposition
What does somatostatin do to insulin and glucagon?
Insulin and glucagon are inhibited by somatostatin
What kind of hormone is insulin?
A peptide hormone
What stimulates insulin secretion?
Secretion is stimulated by a rise in plasma glucose, parasympathetic release of ACh, beta 2 adrenoceptor stimulation (adrenaline) and amino acids arginine and leucine
What inhibits insulin release?
Release is inhibited by low glucose concertrations, noradrenaline (alpha 1) and somatostatin.
How does the posterior pituitary communicate with the hypothalamus?
Via specialised neurons
How is the anterior pituitary connected to the hypothalamus?
Via a portal vascular system
Where are vasopressin and oxytocin synthesised and stored?
Synthesised in hypothalamic neurons.
Stored in posterior pituitary.
What kind of hormones does the posterior pituitary produce? Lipid or water soluble?
Water soluble as they are peptide hormones
What does increased osmolality stimulate?
Release of vasopressin (ADH)
Where does vasopressin act on aquaporin channels?
The DCT
Where is renin secreted from?
The JGA
What does the macula densa do?
Detects Na+ concentration at the DCT
Where is angiotensin I converted to angiotensin II?
The lungs
How quickly does aldosterone work?
It takes hours as it works via intracellular receptors to alter gene trascription
Does Candesartan reduce angiontensin II levels?
No. Candesartan is an angiotensin II receptor blocker. It has no effect on ACE
How does trauma affect glucagon levels?
Increase due to sympathetic stimulation to mobilise glucose stores
Where is adrenaline produced?
The central part of the adrenal gland - the adrenal medulla
What does the adrenal cortex secrete?
- Aldosterone from zona glomerulosa
- cortisol and corticosterone (zona fasiculata)
- androgens such as testosterone (5% from adrenal cortex even though majority is from testes/ovaries), dihydrotestosterone, androstenedione (zona reticularis)
Where is noradrenaline released from?
Adrenal medulla
Where is vasopressin released from?
Synthesised in hypothalamus and released by posterior pituitary
What kind of hormone is vasopressin?
A monopeptide hormone
Where does vasopressin cause selective water reabsorption from?
Via aquaporin channels in the collecting duct
How is adrenaline synthesised?
Noradrenaline is a precursor of adrenaline, so, adrenaline is synthesised by the addition of a methyl group to noradrenaline.
What is the rate limiting step in catecholamine synthesis?
The rate limiting step is the hyroxylation of tyrosine
What do phaeochromocytomas secrete?
They most commonly secrete predominantly noradrenaline, though they can be predominanty adrenaline or dopamine secretors.
Why aren’t beta blockers used in phaeochromocytomas?
This could result in unopposed alpha stimulation by the excess noradrenaline causing profound vasoconstriction.
