Endocrinology Flashcards
Describe 7 of the most common endocrine organs
Hypothalamus/pituitary (in head) Thyroid (in neck) Parathyroid (behind thyroid) Pancreas (in abdomen) Adrenal (on top of kidneys) Ovaries / testes
what are the two types of pituitary glands and what are the basic differences
divided into two lobes
anterior - produces various hormones and controlled by the hypothalamus
posterior - stores various hormones produced by the hypothalamus
which hormones are released from the anterior pituitary and what are they stimulated by for release
GH growth hormone - due to GHRH
ACTH adrenocorticotrophic hormone - due to CRH
FSH follicle stimulating hormone- due to GnRH
LH luteinising hormone- due to GnRH
TSH thyroid stimulating hormone- due to TRH
PRL prolactin - no direct stimulation but under inhibitory effect of hypothalamus
what are the effects of these hormones GH ACTH LH / FSH TSH PRL
growth hormone - skeletal growth, important in children - excess in adults causes acromegaly
adrenocorticotrophin hormone - stimulates adrenals to produce steroids
LH/FSH - stimulate ovaries / etsticales to produce sex hormones (pulsatile)
TSH - stimulates thyroid to produce thyroid hormones
Prolactin - stimulates breast milk production
what are the posterior pituitary hormones and what do they do
ADH - stimulates water reabsorption baby kidneys
Oxytocin - helps uterine contractions during labour
what is made in the intermediate zone
melanocyte stimulating hormone
what does cortisol switch off
switch off release of ACTH and CRH
what does GH release switch off
GH and GHRH
what does thyroid hormones release switch off
TSH and TRH
what do sex hormones switch off
FSH/LH and GnRH
what is the anatomy of the thyroid made up of
midline isthmus
right lobe
left lobe
what cells make up the thyroid gland
cells are arranged in follicles and produce thyroid hormones
also have C cells which produce calcitonin for calcium metabolism
what are the effects of released thyroid hormones
interact with receptors in various organs regulating gene expression and aspects of organ function, interact with heart - too much of these hormones leads to tachycardia
what is the specific mechanism of hormone release from the thyroid gland
T4 (80% - inactive form) is converted to T3 (20% - active hormone) in different organs by deiodinase enzyme
TSH stimulates release of T3 and T4
both T3 and T4 have negative feedback on hypothalamus and pituitary glands
how is calcium metabolism controlled
mainly controlled y 4 parathyroid hormones - also controlled by the kidney (produces secretion and VIT D which helps with absorption of Ca)
the gut which absorbs calcium
bone stores calcium
thyroid gland produces calcitonin which reduces amount of Ca in which over stimulation can lead to osteoporosis (brittle bone)
what is the adrenal gland made up of
90% adrenal cortex
10% adrenal medulla
what is released by the adrenal cortex and what is it stimulated by
stimulated by the pituitary gland produces: corticosteroids (cortisol) androgens (male hormone) mineralcorticocoids (aldosterone - important in the RAS system to control blood pressure)
what is the adrenal medulla stimulated by and what does it release
stimulated by sympathetic preganglionic neurons
releases catecholamines such as A, NA, dopamine - which are related to blood pressure
where are the ovaries situated and what do they contain
either side of the uterus and contain follicles which has the oocyte depending on the stage of maturation
describe the life cycle of FSH and LH release from the ovary
first half of cycle - more FSH secretion from pituitary which means more oestrogen from ovary
second half - more LH secretion form pituitary which means more progesterone
what does inhibin do
negative feedback pituitary gland for FSH and LH
what effect will high levels of oestrogen do to hormones
negative feedback on FSH but positive feedback on LH
it can also either stimulate or inhibit GnRH release from hypothalamus
which cells in the testis produce testosterone
leydig cells
what do seminiferous tubules do
they are the site of germination, maturation and transport of sperm cells within the testes
if testosterone is too high what happens
inhibits hypothalamus via negative feedback which in combination with inhibin inhibit FSH and LH from the pituitary
what is the difference between primary and secondary over/under secretion
primary - problem with gland itself
when there is a problem with the influencer of the gland such as a problem with the pituitary gland telling another gland to produce too many or too little hormone
what is special about a tumour in a gland
it can be present without causing effect on the hormone it produces or its mechanism
what is a static test with thyroid as an example
tests for problems with thyroid, sex glands and prolactin secretion. Can immediately test for primary thyroid problems and can test for T£/4 and TSH levels
how would primary vs secondary differ in the thyroid gland
primary hyperthyroidism then T3 and or T4 is elevated with suppressed TSH
if secondary hyperthyroidism then T3/T4 is elevated with elevated TSH
what is a stimulation test give examples
for suspected hormonal under secretion where the static test is not enough
take blood, give hormone, test again, if individual fails to respond to hormone then gland failure
test for adrenal insufficiency by giving ACTH (synacthen test)
insulin stress test - increases insulin via injection and causes blood sugar levels to decrees making stressful situation on body - hopefully hormonal secretion occurs to try and increase blood sugar such as glucagon
what is a suppression test and give examples
for hormonal over secretion - hormone given should suppress natural production of hormone ie negative feedback
if still present then gland is ver producing - used to test for steroid production and glusgcoe for GH secretion (would switch off in normal situations)
what is over secretion and under secretion usually caused by
over - tumour in the gland
under - gland destruction due to inflammation or autoimmune conditions, infection etc
high hormone but low stimulating hormone =
low hormone and high stimulating hormone =
high hormone and high stimulating hormone =
low hormone and low stimulating hormone =
primary hyper
primary hypo
secondary hyper
secondary hypo
what is a prolactinoma
relatively common - pituitary tumour of prolactin releasing cells
what is the clinical presentation of prolactinoma
galactorrhea (breast milk production) amenorrhoea (irregular or no periods) in women and sexual dysfunction in men - headaches and visual field problems
what are the different in symptoms between a large and a small prolactinoma
small - usually just amenorrhea
large - people can’t see peripheral visual field and tumour on pituitary may compress optic nerve
how would you test and treat for prolactinoma
use static test to test for over secretion or high levels of prolactin or pituitary MRI
given drugs to reduce secretion - don’t usually operate
what could cause high prolactin other than a tumour
drugs stress pregnancy sex nipple stimulation non-functioning pituitary tumour
what are the differences in excess GH in the child vs in the adult
child - gigantism, enlarged hands and feet and excessive growth
adult - acromegaly, effects sex, skeletal muscle, large hands and feet, disproportioned jaw
what are the effects of excess GH
can effect visual field of view as push on optic nerves but can also not
can cause hypertension, diabetes increase cancer risk
how would you test for excess GH
suppression test - glucose given and GH measurements at different times (normally high glucose surpasses GH) - imaging done after to confirm tumour
what is the treatment of over secretion fo GH
surgical removal of tumour - radiotherapy and drugs
if high GH but asymptomatic then no need to remove tumour
what is cushing syndrome and what is it caused by
excess levels of cortisol or excessive ACTH production
can be from a pituitary tumour for ACTH or adrenal tumour for cortisol
what is the clinical presentation of cushing syndrome
growth arrest in children - runs moon like face - acne - excessive body hair - fat around the middle and thin extremities - thin skin, easy bruising
what physiologically can be the symptoms of cushing syndrome
hypetension
diabetes
high risk of infections
poor wound healing
how do you test for cushing syndrome
suppression test
use dexamethasone suppression test - confirms failure to suppress cortisol production
what are the two types of cushing syndrome
adrenal cushing - ACTH suppressed
pituitary cushing - high ACTH
what is the treatment for cushing
surgery
radiotherapy
drugs
can be caused by cancer so treat that first to see symptoms effected
what are the different types of over secretion of thyroid hormone
primary / secondary hyperthyroidism both more common in women secondary due to pituitary TSh secretion graves disease thyroiditis drug induced (amiodarone or lithium)
what is graves disease
makes up 80% of hyperthyroidism cases
autoimmune disorder - antibodies mimic TSH which stimulates thyroid all the time - gland is large and smooth and can be caused by viral infections which triggers genetic condition
what percentage of hyperthyroid ism if causes by toxic of multiple nodules
15%
what is thyroiditis
1%
overstimulation of thyroid hormone due to viral infection leading to inflammation of the thyroid gland
what drug induces hyperthyroidism
amiodarone
used to treat cardiac arrhythmias - huge amount of iodine messes up thyroid
lithium - used in psychiatric disorders
what is the clinical presentation of hyperthyroidism
hyperactivity irritability insomnia heat intolerance increased sweating arrhythmias atrial fibrillation weight loss despite over eating menstrual problems
how would you examine for hyperthyroidism
hand tremor increased sweating fast pulse large goitre (swelling of neck) hard to swallow protrusion of eye balls - caused but fat inflammation behind eyes increasing water - unable to fully close eyes and can't look up
how would you test and treat for hyperthyroidism
thyroid blood test
raised thyroid and suppressed TSH - static test
anti thyroid drugs - radioactive iodine or surgery if cancerous
what happens to children with under secretion of GH
in children causes growth failure which is always treated
in adults you don’t always treat can be asymptomatic or causes depression / tiredness
what is the test and treatment for under secretion of growth hormone
stimulation test needed
glucagon stimulates GH production if no production then deficiency
if no result then do insulin stress test forcing GH secretion
treatment via growth hormone replacements but is expensive
what are the causes of under secretion of cortisol
maybe due to adrenal failure or pituitary failure
patients using steroid for long time could cause negative feedback on pituitary to switch off ACTH
what is the clinical presentation of under active cortisol
failure to grow in children severe tiredness dizziness due to low blood pressure abdominal pain vomiting and diarrhoea
how do you test and treat under secretion of cortisol
stimulation test - synacthen test - give ACTH if primary adrenal failure suspected - give GST or IST if secondary suspected
treatment is replacing missing hormone via tablets - are cheap
failure to diagnose could cause death
what causes thyroid hormone under secretion and who is commonly affected
older ladies
primary is thyroid failure and inability to produce hormone - usually autoimmune or drug induced
secondary is failure to produce TSH usually part of pituitary failure
what are the symptoms of thyroid under secretion
weakness and dry skin, decreased sweating, impaired memory, weight gain and hair loss
how do you diagnose and treat thyroid under secretion
static test
treatment is thyroid hormone replacement (cheap)
T4 is given over T3 as half life is too short so would give symptoms of hyperthyroidism
what causes primary and secondary under secretion in sex hormones of males and females
primary in males - testicular failure - in females = ovarian failure
secondary in both is pituitary failure
what are the clinical signs of sex hormone under secretion in males
erectile dysfunction, reduced libido
what are the clinical signs in women for under secretion of sex hormones
amenorrhea
(but this is very common and could be due to many other things such as problems associated with uterine/ovarian/pituitary/hypothalamic
how is low sex hormone production tested and treated
static test - males testosterone
females - osetsorgen
both - LSH or FH
hormone replacement therapy of pituitary hormone replacement
testosterone can be give as a cream but may rub off onto partner so usually given as injection as not good orally
what causes pituitary failure and how would you diagnose this condition
may be due to large tumour, infarction ie limited blood supply to the gland
usually a combination of multiple hormones so both static and stimulation test required
confirm first with endocrine test eg basal = thyroid/prolactin/sex hormone or dynamic = glucagon/insulin then do MRI imaging
what controls increased parathyroid secretion
calcium and vit D
what are the causes of over stimulation of increased parathyroid
primary hyperparathyroidism, cancer, drugs, high calcium suppresses parathyroid - if doesn’t suppress then problem with gland
what are the signs of over stimulation of parathyroid
present as hypercalcemia - high Ca in blood thirst passing too much urine constipation abdominal pain
what do steroid hormones and Vit D derive from
cholesterol
what do thyroid hormones and catecholamines derive from
amino acids (thyroxine)
how to steroid hormones and thyroid hormones alter cell activity
act via intracellular receptors within the nucleus to alter gene transcription
describe how steroid hormones travel from the blood to take action inside the cell
hydrophobic and lipophilic, travel in blood attached to carrier proteins, dissociate from carrier protein and pass through plasma membrane, where bind to intracellular receptor proteins in cytosol (or nucleus) and go into nucleus, hormone-receptor complex acts as transcription factor (turns on/off genes), mRNA is transcribed, leaves the nucleus (translated into specific protein) which carries out function in target cell, roles include carbohydrate regulation, mineral balance, reproductive functions
describe the physiological production of thyroid hormones
Thyroid hormones, derived from tyrosine, majority in inactive form T3 produced in the peripheral tissues though deiodination of T4, cells concentrate iodine for thyroid hormone synthesis, iodine attached to tyrosine residues on protein named thyroglobulin, synthesised by cross-linking iodotyrosine molecules in thyroglobulin and cutting thyroxine out
describe how thyroid hormones bind and effect cells
Thyroid hormone receptors are two separate genes with slightly different actions to one another, recognition sequence the thyroid hormone recognition element (TRE) in front of various genes of energy metabolism and heart function switched on by thyroid hormones, thyroid hormone receptor with bound thyroid hormone binds to TRE in DNA, binding of hormone determines whether proteins that activate or switch off transcription bind to the complex, can be very complicated as can pair with other transcription factors
how do nuclear hormone receptors bind to DNA inside the cell
Sequences upstream of minimal promoter region which affect transcription are binding sites for nuclear hormone receptors, may increase or decrease transcription, regions are small sequences of 6-10 nucleotides to which factors bind, often two copies with spacer in between, sometimes direct repeats sometimes palindromes
how to nuclear hormone receptors take action to DNA inside the nucleus
Activation is ligand-activated transcription factors, sequence specific DNA binding proteins that regulate co-activator RNA polymerase recruitment to induce transcription at target gene promoters, activated by hormones via direct binding, receptor usually inactive due to inhibitory protein, when ligand binds produces conformational change, inhibitory protein dissociates, hormone-receptor complex binds to DNA and activates transcription, receptors have similar protein structure with very similar DNA binding domain and hormone binding domain making them specific
