BP.16 Drugs and hormones Flashcards
What is a hormone
2) how is this different to a neurotransmitter
chemical secreted from a tissue into blood stream whereby it is carried to non-adjacent sites in the body and exerts effect
2) it is secreted by a neuron directly onto adjacent neurones or tissue
Describe the HPA axis:
include tissue/organs involved then what drug they secrete (when final is cortisol)
1. hypothalamic nuclei (releases CRH) 2. anterior pituitary (releases ACTH) 3. adrenal cortex (releases cortisol
What does cortisol inhibit?
2) What does this set-up?
1)Secretion by hypothalamic nuclei of CRH
and
Secretion by anterior pituitary of ACTH
What stimulates the hypothalamic nuclei in the HPA axis
2) the pancreas to secrete insulin
stress (physical or mental)
2) high blood glucose
Effects of cortisol (5)
Increase and maintain normal glucose levels in blood
Increase gluconeogenesis
decrease in protein synth (amino acid free for gluconeogenesis)
Role in regulating brain function
Immune response/inflammation
Syndrome + disease caused by:
1) cortisol hypersecretion
2) cortisol hyposecretion
1) Cushing’s syndrome, cushing’s disease
2) Adrenal Insufficiency, addison’s disease
Symptoms of cushing’s disease:
buffalo lump, fat redistributed (muscle wasting of arms and legs, increased abdominal fat), poor wound healing, easy bruising
Causes of cushing’s disease:
2) Treatment:
Adrenal or pituitary tumour (Cushing’s Disease)
Side effect of chronic glucocorticoid therapy
2) Removal of tumour
Inhibition of cortisol synthesis by metyrapone
What is the aldosterone formed from?
cortiosterone
how does metyrapone work?
11ß-hydroxylating enzyme can be blocked by metyrapone so decreasing the amount of cortisol available for secretion
Used to treat Cushing’s Syndrome
At high levels cortisol can inhibit A and B
At high levels cortisol can inhibit inflammation and the immune response
What effect does insulin have:
2) what synthesises it?
3) what causes the cells to secrete it
Uptake/storage of glucose (as glycogen)
Inhibits fat breakdown
2) beta-cell of the islets of Langerhans in the pancreas
3) glucose enters beta-cell, glycolysis= ATP, ATP production leads to closure of the ATP sensitive K+ channel (KATP) channel on the cell surface; the subsequent membrane depolarization leads to opening of voltage-gated L-type calcium channels, influx of calcium and the release of insulin
3 disorders of insulin :
- Diabetes mellitus
- insulin hyposecretion
- insulin receptor hyposensitivity
main cause of type 1 DM (insulin dependent diabetes
)
2) Treatment:
Insulin hyposecretion due to a loss of beta-cell
2) Substitute with insulin . one background intermediate acting (e.g isophane insulin) AND one before a meal, short term fast acting (soluble insulin)
what are the different “acting” insulin preparations, describe structure of drug
1) short (soluble)
2) intermediate (in complex with zinc salts as particles)
3) long (in complex with zinc salts as large particles)
How is short acting insulin administered
subcutanous (routine) & iv administration (emergency)
cause of type 1 DM (non-insulin dependent):
2) drug used to treat…
Metabolic demands of obesity, Desensitization of insulin receptors
Pancreatic insufficiencey
2) sulphonylureas
When treating type 1 DM with sulphonylureas, how do they work?
Sulphonylureas (e.g. glibenclamide) block the KATP channels so cause depolarisation and increase insulin secretion independently of glucose levels (need partially functioning beta cells).
Describe the HPA axis:
include tissue/organs involved then what drug they secrete (when final is estrogen and progesterone)
B) describe -ve feedback loop:
1. hypothalamus (releases GRH) 2. pituitary (releases FDH and LH) 3. adrenal cortex b) estrogen and progesterone, inhibit hypothalamus and pituatry
What does estrogen and progerstrone cause?
ovulation
What does 1) GRH, 2) FSH and 3) LH stand for?
1) gonadotrophin releasing H
2) Follicle stimulating H
3) lutenising H
Physiological effects of 1)estrogen and 2)progestrone on endometrium
Estrogen-
sensitises LH releasing cells in pituitary
proliferation of endometrium
Inhibits FSH so regulates cycle
Progestrone-
renders the endometrium suitable for implanting of a fertilized ovum
Inhibits further release of GRH, FSH, and LH so regulates cycle and ovulation
1) If fertilised ovum is implanted how is progesterone secretion maintained?
2) what 2 things does progesterone do?
1) ovum secretes human chorionic gonadotrophin, this stimulates corpus luteum to continue secreting progestrone
2) maintains endometrium and pregnancy
Inhibits further secretion of GRH, FSH, and LH, this prevents further follicles developing (-ve feesback)
What are the 2 main types of oral contraceptives:
Combined oestrogen and progestrone (combined pill)
Progestrone alone (progestrone only pill/minipill)
Oral contraceptives target the ___A__ feedback system clamping secretion of ______B______
A) negative
B) GRH FH and LH
Oral contraceptives target the ___A__ feedback system clamping secretion of ______B______
A) negative
B) GRH FH and LH
How does the combined pill work?
Estrogen inhibits secretion of FSH via –ve feedback, this prevent development of ovarian follicle
Progestrone inhibits secretion of LH, (-ve feedback) prevents ovulation and also makes the cervical mucus less suitable for passage of sperm
How is the combined pill taken?
Taken for 21 days then a 7 pill free period causes withdrawal bleeding (false period)
How does the progesterone only pill work?
2) how is it taken?
3) is it as reliable as the combined pill?
1) Mainly effective due to effect on cervical mucus.
Does not actually blocked ovulation
2) Taken continuously, can cause irregular periods
2) Less reliable than combined pill
What drugs can interact with contraceptives and why?
Broad spectrum antibiotic (e.g. amoxicillin)
Enzyme inducers (e.g Barbiturates, phenytoin, rifampicin) (interact with GABA, enduce cytochrome P450)
How are contraceptives metabolised (3)?
Fraction (variable) of exogenous hormone is conjugated in the liver (glucuronidation), and excreted in bile into duodenum
Gut flora with glucuronidase activity cleave the conjugate allowing reabsorption of active hormone. (may represent significant reservoir)
Broad spectrum antibiotic (e.g. amoxicillin), kill gut flora and so remove this reservoir
