Endocrinology Overview Flashcards
From what molecules can hormones be derived?
- peptide derived
- amino acid derived
- lipid derived
How do water soluble hormones act on target tissues?
bind to receptors on the cell surface
How do lipid soluble hormones act on target tissues?
passively cross the membrane to bind to intracellular receptors
What is a cognate receptor?
a highly selective receptor that recognises a specific hormone
Why is knowing the difference between peptide and protein hormones important?
- production of hormone
- formulation of hormone
- quality assurance of hormone
- drug delivery of hormone
- similar shaped hormones may bind to similar receptors, and cause off target side effects or you get cross reactivity
What are the main routes for hormone delivery to the body?
- injections
- aerosols
- depot injections
ORAL route is not a viable route as proteins would be digested in the GI tract
What are the 3 types of response that a hormone can generate?
- endocrine
- paracrine
- autocrine
What are the different structures of hormones?
- small chemicals/amino acids
- peptides (up to 20 AAs)
- proteins - single chain
- proteins & subunits - multiple units linked together
- complex chemicals
What are examples of peptide hormones?
- Oxytocin
- ADH
How are Oxytocin and ADH synthesised?
- synthesised in the posterior pituitary gland
- 9 amino acids
- only differ from each other by 2 amino acids
(this means that you get cross reactivity, that is, oxytocin has slight anti-diuretic function, and high ADH levels cause uterine contraction)
What are examples of protein hormones?
- Growth Hormone/Prolactin
- FSH / TSH (Thyroid Stimulating Hormone)
- LH / hCG
- Insulin
How are Growth Hormones and Prolactin synthesised?
synthesised in the anterior pituitary gland
How are FSH and TSH structured and synthesised?
HETERO-DIMERIC structures
(two different peptide sequences, combined to make one complex molecule)
- only ONE subunit will bind to the cognate receptor to exert the effect of the hormone
- synthesised in the anterior pituitary
How is insulin structured and synthesised?
- chains are linked by disulphide bonds
- this gives it the specific 3D structure for it to be recognised by the receptor
- produced in the pancreas
What are examples of amino acid hormones?
Tyrosine
- Dopamine
- Noradrenaline
- Adrenaline
- T3/T4
Tryptophan
- Melatonin
How are tyrosine derived hormones synthesised?
Dopamine precursor for Noradrenaline, which is the precursor for adrenaline
Noradrenaline - Adrenaline catalysed by the PNMT enzyme, which is induced by cortisol, the stress hormone
How are tryptophan derived hormones synthesised?
- tryptophan from the diet
- melatonin is derived via serotonin
- synthesised in the pineal gland
What is an example of a lipid hormone?
- steroid hormones e.g. testosterone
How are the lipid derived hormones synthesised and structured?
STERIODOGENESIS
- they all have the same 4C Ring Structure
- many enzymes used, some for more than one part of the pathway (conserved)
- enzymes found in the mitochondria or endoplasmic reticulum of cells
What is a primary endocrine organ?
where the primary function of an organ is to secrete hormones
What is a secondary endocrine organ?
an organ that secreted hormones, but this is not it’s primary function
Name all of the primary endocrine organs
- pineal
- hypothalamus
- pituitary
- thyroid
- parathyroid
- thymus
- adrenal glands
- pancreas
- ovaries
- testes
- placenta
Name all of the secondary endocrine organs
- heart
- stomach
- liver
- kidney
- small intestine
- skin/fat
What are the three endocrine organs of the brain?
- pineal gland - produces melatonin to regulate circadian rhythm
- hypothalamus
- pituitary gland (anterior & posterior)
located deep within the brain - master controllers
Where are the thyroid and parathyroid glands situated?
- sits below the larynx, above the trachea
- shaped like a bow tie
What hormones do the thyroid and parathyroid glands produce?
Thyroid:
T3 and T4 to regulate metabolism
Parathyroid:
produces the parathyroid hormone in response to Calcium changes
produces Calcitonin to help regulate calcium metabolism
Where is the thymus gland?
- located close to the heart
- shaped like a thyme leaf
What hormones does the thymus gland produce?
- peptide hormone THYMOSIN
- stimulates activity of T cells and Antibody production in bone-marrow
- critical for immune function
What is the most common thymus disease?
myasthenia gravis
- overproduction of antibodies
- directed at the nAChR at neuromuscular junctions
Where is the pancreas?
- near the liver
- in the islets of langerhans 1% of the pancreas
- only this 1% is associated with endocrine function, the rest is associated with digestive enzymes
What hormones does the pancreas produce?
- insulin
- glucagon
- somatostatin
- ghrelin
- pancreatic polypeptide
In what three ways do endocrine glands become dysfunctional?
- hyposecretion of hormones
- hypersecretion of hormones
- tumours develop in the endocrine gland
What is the basic outline of the feedback loop?
- Hypothalamus
- Pituitary
- Primary Gland produces a HORMONE
this hormone then feeds back onto both the pituitary and the hypothalamus to inhibit more production