Theme 1 - Endocrine System Flashcards
Do the glands in the endocrine system have ducts?
No they are ductless
Do hormones act upon all cells?
No only those with target tissues
Draw or list the endocrine glands
Hypothalamus Pituitary (Anterior/Posterior) Thyroid ParaThyroid Thymus Kidney Adrenal Pancreas Gonad
Draw and label the hypothalamus/pituitary gland.
Hypothalamus
Hypothalamico-hypophyseal vessel
Infindibulum
anterior/posterior
What is the main function of thyroid and parathyroid
Metabolic rate
calcium homeostasis
What hormone does the pancreas secrete
Insulin
Function of Adrenal medulla and cortex
Medulla -Stress response,
Cortex - Stress, Sodium and glucose
Function of gonads
Secondary sexual characteristics
What are the three main types of hormone receptor?
G protein coupled
Steriod
Tyrosine Kinase
Steroid hormone - Mechanism of action
Crosses membrane
binds to receptor in cytoplasm or nucleus
This complex then influences gene transcription
G protein mechanism of action
Binds to receptor
Synthesis of second messenger CAMP
Second messenger phosphorelates to cause …
Tyrosine mechanism of action
Sometimes dimerised
Hormone binds to receptor
recptor then acts as enzye to influence intracellular activity
What are the characteristics of peptide hormones?
Water solvable Not orally active Rapid onset Protease vulnerable Unable to cross cell membrane without carrier protein Short duration and plasma half life
Characteristics of steriod and thyroid hormones
Lipid soluble Orally active Slow onset Must be protein bound in blood But unbound is biologically active Can cross cell membrane Long duration and half life
Is secretion usually controlled by the anterior or posterior pituitary
anterior
TSH stimulates?
Thyroid - Thyroxine
ACTH stimulates?
Adrenal cortex - cortisol
TRH, from/stimulates?
Hypothalamus/ant pit to relaese TSH
CRH from/stimualtes?
Hyopthalamus to ant pit to relaease ACTH
GnRH from/stimulates?
Hypothalamus to ant pit to release FSH
GHRH from stimulates?
Hypothalamus to ant pit to release growth hormone
How is hormone secretion typically regulated, give an example?
Negative feedback.
eg TRH, TSH, Thyroxine
CRH, ACTH, cortisol
GnRH, FSH, oestrodiol
What hormaones are secreted by the posterior pituitary ?
ADH/vasopressin and Oxytocin
What types of hormone are ADH and oxytocin, where are they synthesised?
Peptide
Synthesised in supraoptic and para-ventricular nuclei of the hypothalamus
What influences the secretion of ADH
Plasma osmolarity.
What affect does ADH have upon the kidney?
Stimulates v2 receptors which cause the translocation of aquaporins to membrane of tubule membrane that lead to water re absorption
How does vasopressin/ADH act upon the vascular system?
Stimulates v1 receptors to cause vasoconstriction.
What influences secretion of oxytocin?
Stimulation of genitals and nipples
What does oxytocin act upon?
Acts via IP3 channes to cause contraction of smooth muscle in breast and uterus.
During pregnancy there is an increase in oxytocin, explain why this dies not result in a premature birth?
Increase in oxytocin paralleled by an increase in oxytocinase. Inhibits the contraction of smooth muscle in uterus.
Explain how the childbirth an oxytocin constitutes a positive feedback loop.
oxytocin causes contraction of smooth muscle in uterus. Foetus pushes against cervix. Stimulation of cervix causes further release of oxytocin leading to further contraction of uterus.
What hormones are secreted by the anterior pituitary?
Growth Hormone Prolactin TSH ACTH FSH LH
What’s the difference between where hormones released from the ant and post pituitary gland are synthesised?
Hormones from post pituitary gland are synthesised in the hypothalamus (supraoptic and paraentricular).
Hormones secreted from ant pituitary gland are synthesised in the ant pituitary.
Where are the following hormones synthesised and by what cells? FSH, ACTH, TSH, proactin, growth hormone
In the ant pituitary by: gonadotrophe, corticotrophe, thyrotrophe and lactotrophe, somatotrophe cells respectively
What hormones inhibits/stimulates prolactin synthesis?
Dopamine inhibits. TRH stimulates.
What non hormonal factors can stimulate prolactin secretion?
Mild stress, nipple stimulation, coitus.
What is the role of prolactin?
Development of breast tissue and lactation.
Is prolactin secreted in males?
Yes
What inhibits and stimulates the release of growth hormone?
GHRH from hypothalamus
GHRIH /somatoststin
How do nutritional factors influence the secretion of growth hormone?
Stimulated by: Increased carbs and amino acids
Decreased amino acids.
In some tissues GH needs to act via second messengers, what are these and where are they produced?
INsulin like growth factor 1 &2. Made in the liver
What is the role of GH? Is
Increase linear growth in adolescence (foetal growth independent of this)
Which part of the adrenal/suprerenal gland is essential for life?
The cortex
What types of hormones are secreted from the adrenal cortex?
glutocorticoids
mineralcorticoids
What steriod hormones are synthesised from cholesterol?
Adosterone
Cortisol
Testerone to androsterone
It it significant that the adrenal glands secrete small amounts of male and female sex hormones?
No, this is only significant in adrenal disorders
When does ACTH secretion peak?
Morning (assuming non shift work)
Stress
What is the typical lad time of cortisol levels in relation to ACTH peak and nadir?
2hrs
What percentage of cortisol in the blood is free and what happens to the rest?
10% free the rest is protein bound.
In the plasma what is cortisol bound to?
10% free
15% albumin
75% corticosteroid binding globulin
What influence does pregnancy have on the levels of corticosteriod binding globulin?
CBG increses but cortisol increases to maintain some level of free cortisol.
Where does the metabolism of adrenal steroids take place?
Liver
How does cortisol influence carbohydrate metabolism?
Antagonises the effects of insulin on cellular uptake of glucose
Stimulates glycogenolysis
Stimulates hepatic gluconeogenesis
What influence does cortisol have on lipid metabolism?
Stimulates lipolysis and mobilisation of fatty acids.
In relation to fat synthesis and disposition, what can excessive levels of cortisol cause?
Increased fat synthesis.
fat deposited around face and inter scapula region and trunk.
What effect does cortisol have on amino protein metabolism?
Stimulates amino acid uptake in liver, leading to gluconeogenesis.
Inhibits amino acid uptake in periphery
How does cortisol influence blood pressure?
Enhances vasoconstrictor response to catechloamines, which then increases blood pressure.
What are the psycholgical effects of glutocosteroids ?
Elation and sedation
How do glutocorticoids affect immune response?
They suppress the lymphoid tissue, reduce the antibody production and inhibit the cellular immune system.
• They stabilize leucocyte membranes and reduce the release of proteolytic enzymes.
• They inhibit phospholipase A2 and reduce the synthesis of the inflammatory mediators.
Name 2 mineralocorticoid
Aldosterone and 11-deoxycorticosterone
What is the major controlling factor of aldosterone?
Renin angiotensin system
Other than renin-angiotensin, what other factors influence aldosterone?
Stimulated by: Trauma anxiety Hyperkalemia Hyponaturemia Inhibited by: atrial natriuric peptide
Within the circulation how much aldosterone is protein bound?
50%
Aldosterone mechanism of action?
intracellular receptors which cause expression of ion channels that transport sodium and potassium ions across the cell membrane
Upon what part of the kidey does aldosterone affect reabsorption?
distal tubule
To a lesser extent what tissues does aldersterone affect sodium reabsoption?
Loop of Henle collecting duct proximal tubule colon sweat glands salivary glands
Pharma uses of adrencorticosteroids (hydrocartisone)
Asthma, allergies, arthritis
What type of therapy are mineralocorticoids used for?
replacement therapy
What is used to replace aldersterone and why?
fludricortisol, because aldosteron has a short half life
What are the adverse affects of glucocortioids?
Steroid usage may suppress wound healing and may exacerbate infections due to their immunosuppresant effects.
Long term use in children may cause inhibition of growth, and in adults may result in osteoporosis.
The development of diabetes mellitus and other symptoms of Cushing’s syndrome also often accompanies steroid therapy.
Adverse chronic effect of glucocorticoid and explain this
Chronic administration of exogenous glucocorticoids results in suppression of ACTH secretion leading to atrophy of the adrenal cortex.
Why would it be a bad idea for a pt to suddenly stop long term steriod therapy?
If steroid therapy is then stopped abruptly, the adrenal cortex is unable to secrete endogenous hormones and the patient suffers an Addisonian crisis, which may be fatal. This consequence overcome by the gradual reduction of the dose of the exogenous steroid
Within the thyroid what is the function of the colliods
reserviour for thyroid hormone
Thyroid hormones are especially important for the development of the CNS, what aspect in particular
The mylenation of nerve fibres
By what primary mechanism do thyroid hormones increase metabolic rate?
Increase number and size of mitochondria, increase in metabolic enzymes
Thyroid hormones increase basal metabolic rate, and therefore oxygen consumption, in nearly every organ except?
Brain Uterus Testes Spleen Thyroid gland Anterior pituitary gland
What is levothyroxine used to treat and how is it administered?
treat thyroid deficiency. It can be used to suppress TSH secretion in the treatment of some thyroid tumours. It can be given by mouth or by injection.
Where is levothyroxine metabolised and what are the adverse effects associated with it?
Liver
palpitations, arrhythmias, diarrhoea, insomnia, tremor, weight loss
name two anti thyroid drugs
carbimazole
methimazole
potassium perchlorate
How can nuclear medicine be used to reduce thryroid hormaone secretion
Iodine 131 (raduioactive isotope) actively taken up by thyroid. This in turn will damage cells and reduce secretion.
What is carbimazole and its mechanism of action?
anti thyroid drug - used to treat hyperthyroidsim.
Converted into methimazole. Prevents synthesis if T3 and T4.
Adverse effects of carbimazole?
Rashes and pruritus are common which can often be treated with antihistamines. The most serious rare side effect is neutropenia and agranulocytosis. Teratogenic.
What is Propylthiouracil and its mechanism of action?
Used to treat hyperthyroidism. Inhibits thyroid hormone synthesis. can be used in first trimester
Adverse effects of Propythiouracil?
Rashes and pruritus are common which can often be treated with antihistamines. Its notable side effects include a risk of agranulocytosis and risk of serious liver injury, including liver failure and death
Goitre?
Enlargement of thyroid gland
Primary hypothyroidism
problem with thyroid
Secondary hypothyroidism
Problem with pituitary
Hypothyroidism Symptoms
May be none Lethargy Mild weight gain Cold intolerance Constipation Facial puffiness Dry skin Hair loss Hoarseness Heavy menstrual periods
Severe hypothyroidism: signs
Change in appearance eg face puffy and pale Periorbital oedema Dry flaking skin Diffuse hair loss Bradycardia Signs of median nerve compression (carpal tunnel) Effusions, eg ascites, pericardial Delayed relaxation of reflexes Croaky voice Goitre Rarely stupor or coma
Causes of Primary Hypothyroidism
Autoimmune
iatrogenic
Thyroiditis
Drugs (e.g. lithium
treatment for primary hypothyroidism?
Thyroxine
What is Hasimoto’s disease?
Chronic autoimmune thyroisitis
Symptoms of thyrotoxicosis?
Weight loss Lack of energy Heat intolerance Anxiety/irritability Increased sweating Increased appetite Thirst Palpitations Pruritus Weight gain Loose bowels Oligomenorrhoea