Endocrinology Overview Flashcards
1
Q
From what molecules can hormones be derived?
A
- peptide derived
- amino acid derived
- lipid derived
2
Q
How do water soluble hormones act on target tissues?
A
bind to receptors on the cell surface
3
Q
How do lipid soluble hormones act on target tissues?
A
passively cross the membrane to bind to intracellular receptors
4
Q
What is a cognate receptor?
A
a highly selective receptor that recognises a specific hormone
5
Q
Why is knowing the difference between peptide and protein hormones important?
A
- 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
6
Q
What are the main routes for hormone delivery to the body?
A
- injections
- aerosols
- depot injections
ORAL route is not a viable route as proteins would be digested in the GI tract
7
Q
What are the 3 types of response that a hormone can generate?
A
- endocrine
- paracrine
- autocrine
8
Q
What are the different structures of hormones?
A
- small chemicals/amino acids
- peptides (up to 20 AAs)
- proteins - single chain
- proteins & subunits - multiple units linked together
- complex chemicals
9
Q
What are examples of peptide hormones?
A
- Oxytocin
- ADH
10
Q
How are Oxytocin and ADH synthesised?
A
- 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)
11
Q
What are examples of protein hormones?
A
- Growth Hormone/Prolactin
- FSH / TSH (Thyroid Stimulating Hormone)
- LH / hCG
- Insulin
12
Q
How are Growth Hormones and Prolactin synthesised?
A
synthesised in the anterior pituitary gland
13
Q
How are FSH and TSH structured and synthesised?
A
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
14
Q
How is insulin structured and synthesised?
A
- 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
15
Q
What are examples of amino acid hormones?
A
Tyrosine
- Dopamine
- Noradrenaline
- Adrenaline
- T3/T4
Tryptophan
- Melatonin
16
Q
How are tyrosine derived hormones synthesised?
A
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
17
Q
How are tryptophan derived hormones synthesised?
A
- tryptophan from the diet
- melatonin is derived via serotonin
- synthesised in the pineal gland
18
Q
What is an example of a lipid hormone?
A
- steroid hormones e.g. testosterone
19
Q
How are the lipid derived hormones synthesised and structured?
A
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
20
Q
What is a primary endocrine organ?
A
where the primary function of an organ is to secrete hormones
21
Q
What is a secondary endocrine organ?
A
an organ that secreted hormones, but this is not it’s primary function
22
Q
Name all of the primary endocrine organs
A
- pineal
- hypothalamus
- pituitary
- thyroid
- parathyroid
- thymus
- adrenal glands
- pancreas
- ovaries
- testes
- placenta
23
Q
Name all of the secondary endocrine organs
A
- heart
- stomach
- liver
- kidney
- small intestine
- skin/fat
24
Q
What are the three endocrine organs of the brain?
A
- pineal gland - produces melatonin to regulate circadian rhythm
- hypothalamus
- pituitary gland (anterior & posterior)
located deep within the brain - master controllers
25
Where are the thyroid and parathyroid glands situated?
- sits below the larynx, above the trachea
| - shaped like a bow tie
26
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
27
Where is the thymus gland?
- located close to the heart
| - shaped like a thyme leaf
28
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
29
What is the most common thymus disease?
myasthenia gravis
- overproduction of antibodies
- directed at the nAChR at neuromuscular junctions
30
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
31
What hormones does the pancreas produce?
- insulin
- glucagon
- somatostatin
- ghrelin
- pancreatic polypeptide
32
In what three ways do endocrine glands become dysfunctional?
- hyposecretion of hormones
- hypersecretion of hormones
- tumours develop in the endocrine gland
33
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
34
Where are the ovaries located?
- pelvic cavity
35
What hormones do the ovaries produced?
- steroids: oesterogen and progesterone
| - protein: inhibit and relaxin
36
How are the ovaries regulated?
by the FSH and LH secreted from the anterior pituitary
37
Where are the testes located?
in the scrotum
38
What hormones do this testes produce?
```
steroid hormones (androgens)
- mainly testosterone
```
for spermatogenesis
39
How are the testes regulated?
by the FSH and LH secreted from the anterior pituitary
40
Where is the placenta located?
links a developing foetus to a maternal uterine wall
41
What hormones does the placenta produce?
Steroid Hormones:
- Oestrogen
- Progesterone
Protein Hormones:
- Chorionic Gonadotrophin (CG)
- Corticotropin Releasing Hormone (CRH)
- Placental Lactogenic (PL)
42
What hormones are produced by the heart (a secondary endocrine organ)?
atrial natriuretic peptide
- stimulates the kidney to excrete more salt
- decreases excess blood volume
43
What secondary endocrine organ is the largest?
GI Tract, produces over 30 hormones
44
What hormones are produced by the kidney (a secondary endocrine organ)?
Juxtaglomerular Cells secrete Renin (indirectly signals the adrenal cortex to secrete aldosterone)
Erythropoietin to increase RBC production
45
What hormones are produced by the skin (a secondary endocrine organ)?
Vitamin D
| important for calcium absorption
46
Where is the hypothalamus located?
- below the thalamus
| - above the brain stem
47
Where is the pituitary gland located?
- small bony cavity (a part of the skull known as sella turcica) below the hypothalamus
- connects to the hypothalamus via the infundibulum, the pituitary stalk
48
What neurones are associated with the anterior pituitary?
parvicellular neurones - short neurones
49
How does the hypothalamus communicate with the anterior pituitary?
via the portal system
- circulatory link
short neurones secrete regulatory hormones into the portal system to be carried to the anterior pituitary to exert control
hypothalamic-pituitary portal system
50
What neurones are associated with the posterior pituitary?
magnocellular neurones - longer neurones
- supraoptic neurons
- paraventricular neurones
51
How does the hypothalamus communicate with the posterior pituitary?
neurones produce the hormones, carried down through the nerve axon to the nerve terminal
hormones are released at the terminal, diffuse into the capillary network of the posterior lobe
DO NOT ENTER THE PORTAL SYSTEM - as with the anterior pituitary
- a direct neuro-endocrine link
52
What are the regulatory hormones secreted from the hypothalamus that act on the anterior pituitary?
(FLAT PiG)
- GNRH (Gonadorelin) - FSH and LH
- CRH - ACTH
- TRH - TSH
- Prolactin Releasing/Inhibiting Hormone - Prolactin/Dopamine
- GHRH/GHIH (Somatostatin) - Somatotropin Growth Hormone
53
What kinds of molecules are the hormones that are released by the hypothalamus and pituitary gland?
they are ALL peptides/small proteins
| - except for dopamine, which is an amino acid derivative of tryptophan
54
What is a tropic hormone?
a hormone that then acts on another primary endocrine gland
```
+ = causes release of a hormone from a gland
- = inhibits the release of a hormone from a gland
```
55
What hormones secreted from the anterior pituitary are tropic?
- FSH & LH
- Adrenocorticotropin Hormone
- Thyroid Stimulating Hormone
56
What hormones secreted from the anterior pituitary are non-tropic?
- Prolactin
| - Growth Hormone
57
What are the hormones that are released from the posterior pituitary?
- Oxytocin
| - ADH (Anti Diuretic Hormone), Vasopressin
58
How is FSH and LH secreted from the anterior pituitary?
Gonadotropin Releasing Hormone, GONADORELIN
released from the hypothalamus
acts on Gonadotropes to secrete the FSH and LH
these then travel to the gonads to produce sex hormones
- ovaries
- testes
= tropic hormones
59
How is Adrenocorticotropin Hormone (ACTH) secreted from the anterior pituitary?
Coricotropin Releasing Hormone
released from the hypothalamus
acts on Corticotropes to secrete adrenocorticotropin hormone that then travels to the adrenal cortex
= tropic hormone
- cortisol
- aldosterone
60
How is Thyroid Stimulating Hormone secreted from the anterior pituitary?
Thyrotropin Releasing Hormone released from the hypothalamus
acts on Thyrotropes to secrete Thyroid Stimulating Hormone that then travels to the thyroid gland
= tropic hormone
61
How is Prolactin secreted from the anterior pituitary?
Prolactin Releasing Hormone (theoretical hormone)
released from the hypothalamus
acts on Lactotrophes to secrete Prolactin that then acts on breast tissue
= non-tropic hormone
this secretion is INHIBITED by the Prolactin Inhibiting Hormone, Dopamine
62
How is Growth Hormone secreted from the anterior pituitary?
Growth Hormone Releasing Hormones released from the hypothalamus
acts on Somatotropes to secrete Growth Hormone (somatotropin) that then acts on the liver and other cells
= non-tropic hormone
this secretion is INHIBITED by the Growth Hormone Inhibiting Hormone, Somatostatin
63
What is the HP _ Axis?
where an environmental influence will cause the hypothalamus to secrete a regulatory hormone
this then travels to the pituitary to cause the release of a specific hormone
tropic: hormone will then act on another primary gland to produce another hormone to exert it's effect on the body
non-tropic: hormone from the pituitary then acts on the body
64
What is a feedback loop?
control of the endocrine system via multiple feedback loops (where hormone act back on the pituitary/hypothalamus) in eat of the separate axes
65
What is the short loop feedback mechanism?
where the hormones secreted from the primary endocrine gland, acts back on the anterior pituitary to inhibit the secretion of the hormone there
66
What is the long loop feedback mechanism?
where the hormones secreted from the primary endocrine gland, acts back on the hypothalamus to inhibit the secretion of the regulatory hormone
67
What is the ultra-short loop feedback mechanism?
where the regulatory hormone secreted from the hypothalamus, acts directly back on the hypothalamus to inhibit the secretion of the regulatory hormone itself
68
What is the most common prolactin disease?
a tumour of the lactotropes cells in the pituitary
treated by using dopamine receptor agonists (as this is the natural inhibitor of prolactin)
- bromocriptine/cabergoline
69
What are the conditions associated with hyper-secretion of Growth Hormone?
hyper-secretion caused by a tumour in the pituitary
- Children: Gigantism (before the long bones have fused)
- Adults: Acromegaly
70
What is the treatment for the hyper-secretion of Growth Hormone?
Growth Hormone Inhibiting Hormone (Somatostatin)
- formulate an analogue to increase half-life:
Sandostatin (90 min T1/2 instead of 3 mins)
71
What are the two different forms of deficiency of Growth Hormone?
- lack of production (pituitary dwarfism)
| - hormone resistance (laron dwarfism)
72
What are the causes of lack of production of growth hormone in pituitary dwarfism?
- Tumour (that blocks signalling by pressing on the infundibulum), Craniopharyngioma most common
- Mutation of genes
- Head injury/infection
- Radiotherapy
73
What are the causes of hormone resistance to growth hormone in laron dwarfism?
- GH binding protein mutated (so that the hormone cannot be transported in the blood)
- GH receptor mutations on the target tissues
74
What types of hormone are oxytocin and vasopressin (ADH)?
small peptide hormones, 9 amino acids
| differ from each other by 2 amino acids
75
What are the three functions of oxytocin?
- stimulation of milk ejection (not production, because this is prolactin)
- stimulation of uterine smooth muscle contraction at birth
- establishment of maternal behaviour (love hormone)
76
Explain how oxytocin in the stimulation of uterine muscle is an example of positive feedback
- pressure from the baby on the cervix
- sensed by sensory nerves
- information relayed to the hypothalamus
- oxytocin is released from hypothalamic cells
- oxytocin travels in the blood
- binds to a receptor to cause uterus contraction
- contraction causes more pressure to be put on the cervix
- sensory nerves sense the pressure
- releases more oxytocin
oxytocin release stops, when the baby is expelled and there is no more pressures on the cervix
77
What is the drug Pitocin used for?
it is SYNTHETIC oxytocin to induce labour and speed up contractions
- monitoring required:
contractions that are too strong/quick may reduce the blood supply to the baby
78
What is the role of vasopressin (ADH) in the body?
water regulation
- binds to receptors in the collecting duct and distal convoluted tubules
- causes aquaporin II channels to be inserted into the membrane
- this allows for water reabsorption
- these membranes are impermeable to water without these channels
79
What is diabetes insipidus and what are the two main causes?
involves vasopressin, where there is excessive urine production
- Hypothalamic Central Diabetes Insipidus
- Nephrogenic Diabetes Insipidus
80
What is Hypothalamic Diabetes Insipidus?
```
deficiency in the vasopressin SECRETION
caused by:
- head trauma
- infections
- tumours
treat with:
- exogenous vasopressin
```
81
What is Nephrogenic Diabetes Insipidus?
where there is INSENSITIVITY to vasopressin in the kidney
caused by:
- renal disease
- mutations in the vasopressin receptor gene
- mutations in the aquaporin II gene
treat with:
- increasing water consumption (incentive to vasopressin, cannot give exogenously)
82
Where is the pineal gland located and what is it's structure?
- in the epithalamus, between the 2 hemispheres in the centre of the brain
- 6mm in size
- pinealocytes secrete melatonin
- melatonin maintains circadian rhythm
83
How does melatonin work?
- production of melatonin is inhibited by light to the retina
- production is permitted by darkness
- melatonin can help with sleep disorders:
seasonal affective disorder (winter depression)
insomnia
