Endocrine system Flashcards
What are the 6 main endocrine glands in the body?
1) Hypothalamus/pituitary
2) Pancreas
3) Ovaries/Testes
4) Parathyroid
5) Thyroid
6) Adrenal
Which gland controls most of the glands in the body?
The small pituitary gland
Which gland controls the pituitary gland?
The hypothalamus
What are the 2 functional lobes of the pituitary gland and what do they produce?
1) Anterior pituitary: produces various hormones
2) Posterior pituitary: doesn’t produce any hormones just stores those produced by the hypothalamus
What are the 5 main hormones produced by the anterior pituitary and what do they do?
1) TSH: stimulates the thyroid gland to produce thyroid hormone
2) ACTH (adrenocorticotrophic hormone): stimulates the adrenal glands to produce steroids
3) Gonadotrophins (FSH/LH): stimulates the testes or ovaries to produce sex hormones
4) GH (growth hormone): for skeletal growth
5) Prolactin (PRL): stimulates breast milk production
What 2 hormones are stored in the posterior pituitary (Which have been produced by the hypothalamus)?
1) Antidiuretic hormone (ADH): stimulates water reabsorption by the kidneys
2) Oxytocin: Helps uterine contractions during labour
What hormones are secreted by the hypothalamus to control the secretion of GH, TSH, ACTH and gonadtrophins from the anterior pituitary?
1) GHRH/GRH (growth-hormone releasing hormone): stimulates the release of GH
2) CRH (corticotrophin release hormone): stimulates the release of ACTH
3) TRH (thyrotrophin releasing hormone): stimulates the release of TSH (Thyroid stimulating hormone)
4) GnRH (gonadotrophin releasing hormone): stimulates the release of FSH and LH (gonadoptropins)
How is the release of prolactin from the anterior pituitary controlled?
No prolactin releasing hormone exists, instead it is under inhibitory control of the hypothalamus which continually secretes an inhibitor, after birth inhibitor stops being released and prolactin levels increase
How are pituitary hormones and hormones from the hypothalamus switched off?
By negative feedback systems
1) Cortisol feeds back to switch of ACTH and CRH
2) Thyroid hormones feedback to switch off TSH and TRH
3) Sex hormones feedback to switch off FSH and LH and GnRH
4) Growth hormone switches of GH and GHRH
Name 4 glands which are not controlled by the pituitary gland and what they produce?
1) Adrenal medulla: produces ADR and NA (nb. adrenal cortex which releases cortisol is controlled by pituitary)
2) Pancreas: secrets insulin, glucagon (and somatostatin)
3) Gut hormones
4) Parathyroid (controls calcium levels)
What is the rough gross structure of the thyroid gland?
2 lobes (R+L) and a midline isthmus (middle lobe, just below the circoid cartilage)
Which cells of the thryoid gland are not controlled by the pituitary and what do they secrete?
C cells, secrete calcitonin (involved in calcium metabolism) - they are not controlled by the pituitary!
How many parathyroid glands are there?
4
Other than the parathyroid glands what are the 3 other organs involved in calcium metabolism?
1) Kidneys: calcium excretion and production of Vitamin D
2) Gut: absorption of calcium
3) Bone: storage of calcium
Corticosteroids (cortisol), androgens (male hormones) and mineralcorticoid (aldosterone) are produced by which part of the adrenal gland, under control of what?
Adrenal cortex
Cortisol and androgens under control of pituitary
Aldosterone related to RAAS
NB. adrenal glands are reason females produce some male hormone
Adrenal cortex makes up how much of the adrenal gland?
90% cortex, 10% medulla
GnRH is secreted in what kind of pattern?
Not continuous but pulsatile
What is the effect of continuous GnRH secretion?
Can lead to suppression of secretion of FSH and LH (can be used therapeutically, if want to stop FSH and LH secretion then can give GnRH continuously)
What hormone is secreted from the pituitary gland for the first 14 days of the menstrual cycle and what does this cause to be released?
FSH for first 14 days
Causes increased oestradiol secretion from ovaries
What 3 things are the testes composed of and what do they produce?
1) Interstital or leydig cells: produce testosterone
2) Seminiferous tubules: made up of germ cells producing sperm
3) Sertoli cells: producing inhibin
Both testosterone and inhibin have an inhibitor effect on the release of FSH and LH from the pituitary
What is primary hormonal oversecretion/undersecretion?
Problem with the gland itself (no problem with the pituitary)
What is secondary hormonal oversecretion/undersecretion?
Problem with the pituitary gland making the gland itself overactive or pituitary gland not sending signals to the gland (nb. a secondary problem in a gland would be a primary problem in the pituitary gland)
What is tertiary hormonal oversecretion/undersecretion?
Problem with the hypothalamus however this is very rare
What glands are static tests used to find abnormalities in?
Thyroid gland
Sex glands
What is a static test in terms of measuring endocrine abnormalities?
Measurement of the levels of hormones in the blood at any one time (also called spot tests)
Which hormones are tested for in suspected hyperthyroidism and what do the results tell you?
Static Test for T3/T4 and TSH
IF T3/T4 high but TSH is suppressed = primary hyperthyroidism
If T3/T4 high and TSH also high = secondary hyperthyroidism
Which hormones are tested for in suspected hypothyroidism and what do the results tell you?
Static test for T3/T4 and TSH
If T3/T4 low but TSH is elevated = primary hypothyroidism
If T3/T4 low and TSH also low = secondary hypothyroidism
What hormones are tested for in suspected hypogonadism and what do the results tell you?
Static test for testosterone/oestradiol, FSH and LH
If testosterone/oestradiol low but FSH and LH high = primary hypogonadism
If testosterone/oestradiol low but FSH and LH also low = secondary hypogonadism
With both primary and secondary hypogonadism you get sexual dysfunction
When are stimulation tests used in endocrinology?
Used for suspected hormonal UNDERSECRETION when a static test is not enough (eg. growth hormone deficiency or cortisol deficiency)
Why are static tests not sufficient to measure overproduction or underproduction of GH and cortisol?
Levels fluctuate throughout the day
Normal ranges are different in different people
What test is used for suspected adrenal insufficiency?
Synacthen test
Give patient ACTH, if they fail to respond to the stimulation, ie dont increase production of cortisol then primary adrenal failure is diagnosed
What are glucagon stimulation tests and insulin stress tests for and how do they work?
Used to test for suspected pituitary failure (could be causing low GH and Secondary adrenal failure)
Hypoglycaemia is a stressful event for the body, low blood sugar should cause pituitary to produce GH and ACTH
Glucagon stimulation: give glucagon (to simulate hypoglycaemia) and see if levels of GH and ACTH (and thus cortisol) rise - seen as safer than insulin stress test
Insulin stress test- give insulin to lower blood glucose and see if levels of GH and ACTH (and thus cortisol rise) - insulin stress test is considered gold standard for diagnosing pituitary problems
What is a suppression test used for in endocrinology?
Suspected hormonal over secretion when a static test is not enough eg. suspected adrenal oversecretion of GH over secretion
How do you test for suspected cortisol overproduction?
Suppression test
Give exogenous steroids (eg. dexamethasone) and this should switch off production of endogenous steroids (NB. the steroid must not be detected by your test)
If cortisol production is not suppressed then you need further tests to determine if the problem is primary or secondary)
How do you test for suspected growth hormone overproduction?
Suppression test
Give glucose and test for GH secretion
Glucose should switch of GH secretion in normal individuals
What is a common reason for over secretion of glands?
Benign tumours - could be hyperplasia of gland or autoimmune conditions aswell (eg. thyroid disease)
What is a common reason for under secretion in glands?
Inflammation (including autoimmune conditions) and infarction (no blood supply)
What is a prolactinoma (micro and macro) and what does it cause?
Prolactinoma is a piruitary tumour secreting prolactin
>1cm = macro prolactinoma
What is the clinical presentation of prolactin oversecretion?
1) Galactorrhoea (breast milk production)
2) Amennorrhoea in women and sexual dysfunction in men (large tumour affects other hormones produced by pituitary)
3) Headaches and visual problems in large tumours (any head tumour can cause headaches - visual defects - optic nerve above pituitary - tumour grows and suppresses optic nerve) classically get bitemporal heminaopia (tunnel vision)
What tests or scans need to be done for a diagnosis of prolactinoma?
1) Static test (be aware however that stress can increase prolactin levels)
2) MRI of the pituitary gland
Other than prolactinoma what stimuli can lead to increased pro lactin levels?
1) Sexual intercourse
2) Nipple stimulation
3) Stress
4) large number of drugs
5) pregnancy
6) non functioning pituitary tumour (compressing the hypothalamus and interfering with the inhibitory effect on prolactin secretion)
What is the standard treatment of prolactinomas?
Treated medically
Are the only over secreting pituitary tumours which can be treated medically as they very rarely require surgical intervention (so important to know if dealing with a non functioning pituitary tumour or a prolactinoma)
In adults agromegalic face, wide and large hands/feet and increased sweating are signs and symptoms of what endocrine problem?
GH oversecretion
What tests or scans are needed for a diagnosis of GH oversecretion?
Suppression test needed
Imaging necessary to confirm the presence of a pituitary tumour
What is the treatment for GH oversecretion?
1) Surgical removal of tumour
2) Radiotherapy and medical therapy as surgery doesn’t always remove the whole tumour
What is Cushing’s syndrome?
Steroid overproduction
What could be the causes of steroid over production?
1) Pituitary tumour secreting ACTH (Cushings disease)
2) Adrenal tumours secreting cortisol
3) Some cancers produce ACTH
Moonlike face, acne, hirsutism (abnormal facial or body hair growth), fat redistribution (truncal obesity, thin extremeties), skin abnormalities (thin skin, easy bruising and striae on abdomen) and hypertension and DM are clinical signs of which endocrine problem?
Cushing’s syndrome
What tests are needed for Cushing’s syndrome?
As mentioned, static test not enough, need a suppression test - dexamethasone suppression test
To distinguish between adrenal and pituitary cushing’s use ACTH - if ACTH is suppressed, problem with adrenal gland - failure to suppress ACTH = problem with pituitary (but could also be cancer)
What is the treatment of Cushing’s syndrome?
Pituitary and adrenal: surgery, radiotherapy and or medical treatment may also be required in pituitary disease
Cancer related: treat original cancer
What are the 5 causes of hyperthyroidism?
In order of prevelance
1) Graves disease (autoimmune)
2) Toxic nodule or toxic MNG (multinodal goitre)
3) Thyroiditis (inflammation due to virus)
4) Drug induced (amiodarone - used in cardiology)
5) Rarities
Hyperactivity, insomnia, irritability, heat intolerence and increased sweating, palpitations, weight loss despite overeating, menstrual problems are signs and symptoms of which endocrine problem?
Hyperthyroidism
What is thyrotoxicosis?
another word for hyperthyroidism
In the surgery what 3 things could be examined if suspected hyperthyroidism?
1) Increased sweating, feel for sweaty palms
2) Hand tremor
3) Fast pulse
How is the thyroid gland inspected?
Use atleast 3 fingers either side and ask the patient to swallow, feel for whether the thyroid gland is enlarged
In an thyroid gland examination, an enlarged thyroid gland which is a) Smooth and symmetrical, b) nodular and irregular and c)tender would suggest what cause of the hyperthyroidism?
a) smooth and symmetrical = graves’ disease
b) nodular and irregular = toxic nodule(s)
c) tender = thryoiditis
What is lid lag and what kind of endocrine problem does it present with?
When the eyes follow a finger as it moves downwards, there is a lag of time before the eyelids move down too
Present in Graves disease
Why may problems with swallowing and breathing occur in hyperthyroidism?
massive goitre can cause problems with swallowing and breathing
what are the 3 eye problems which can be associated with Grave’s disease?
Affects around 50% of sufferers
1) Swelling around the eyes
2) Protrusion of the eye ball (proptosis)
3) Paralysis of the eye muscles (patients have double vision)
What is the basic pathophysiology behind graves disease, why does it produce a goitre and why does it affect the eyes?
In graves disease, Ab produced act like TSH
Ab produced can affect eye muscles - hence the eye problems
TSH also leads to growth of the thyroid gland therefore so do the Ab and you get a goitre
What is the treatment for hyperthyroidism?
1) Anti thyroid drugs (if diagnosis is grave’s then 50% go into remission after 6-18 months, if toxic nodules then dont)
2) Radioactive iodine (iodine important in thyroid hormone production, accumulates in the thyroid gland and destroys it)
NB. Anti thyroid drugs in minority of cases can suppress white cell production so if patients get any flu like symptoms then white cell count should be measured immediately
What is the treatment for GH deficiency?
1) Growth hormone replacement injections - but expensive so choose adult patients carefully
What are the signs of GH deficiency in children and adults?
Children: stunted growth
Adults: usually nothing but can feel tired and depressed (these are the ones you choose to replace GH in)
Failure to grow in children, dizziness (due to low BP) and severe tiredness, abdominal pain, vomiting and diarrhoea is the clinical presentation of which endocrine problem?
Steroid under secretion
How can adrenal failure be caused by the use of exogenous steroids?
Exogenous steroids suppress the secretion of endogenous steroids, if exogenous steroids are taken away too quickly then you can get adrenal failure (can only occur for a short time)
What test follows the synacthen test if adrenal insufficiency is suspected?
Glucagon stimulation test or insulin suppression test (except in the very ill as cortisol will be high normally - so if suppression test shows very low cortisol then suppression test may be enough)
What is the treatment for steroid under secretion?
Replace missing hormone with tablets - cheap
In cases where steroid undersecretion is suspected as this is very dangerous then a cortisol injection should be given before any tests even carried out
What are the 2 main causes of primary hypothyroidism?
1) Autoimmune in nature
2) Can be drug induced (lithium can cause it)
What is the usual cause of secondary hypothyroidism?
Usually part of a complete pituitary failure, (ie. if pituitary fails its likely to result in deficiencies of more than 1 hormone)
Weakness, constipation, sensation of cold, decreased sweating, dry skin, weight gain and hair loss and clinical signs and symptoms of which endocrine problem?
Severe hypothyroidism
What is the treatment for hypothyroidism?
Thyroid hormone replacement
What is primary hypogonadism in males and females?
Males - testicular failure
Females - ovarian failure
What is the clinical presentation of hypogonadism in males and females?
Males: erectile dysfunction and reduced libido
Females: menstrual abnormalities (amenorrhoea)
What is the difference between primary and seondary amenorrhoea?
Primary = patient has never had a period Secondary = patient had periods and then they stopped
What is often the cause of amenorrhoea in athletes?
Tertiary hypogonadism (problem with hypothalamus)
What is the treatment of hypogonadism?
1) Hormone replacement therapy
2) Pituitary hormone replacement
(depending on whether primary or secondary)
What are the 2 common causes of pituitary failure?
1) Large tumour (eg. could have a GH secreting tumour so GH is high but tumour is suppressing production of other hormones by the pituitary)
2) Infarction (pituitary tissue dies)
What are basal tests and dynamic tests used in the investigations of suspected pituitary failure and what test would follow these biochemical tests?
Basal tests: thyroid function (T3,T4,TSH), Prolactin, E2 (testosterone and oestradiol)
Dynamic tests: gluagon stimulation test, insulin stress tests
What are the 3 more common causes of increased PTH (parathyroid hormone) production?
1) Primary hyperparathyroidism
2) cancers (some cancers produce a hormone similar to PTH - this can cause hypercalcemia - called secondary hyperparathyroidism)
3) Drugs
What is the clinical presentation of hypercalcemia?
1) Thirst and passing too much urine (osmotic symptoms)
2) Constipation and abdominal pain
How do you test for hyperparathyroidism and what do the results tell us?
Measure calcium and PTH in the blood
High calcium and inappropriately high PTH = primary hyperparathyroidism
High calcium and suppressed PTH = no problem with the parathyroid gland, could be cancer
What are thyroid peroxidase antibodies (TPO) and thyroid stimulating hormone receptor antibodies (TSHR)?
Antibodies which are raised in the majority of patients with graves disease
Tests for these are not routine and are reserved for cases where the diagnosis is unclear
When is surgery used in graves disease?
Saved for contraindicated or failed therapy patients or people with a massive gotire which is suppressing breathing
What are the possible complications of surgery for Graves disease?
1) Hypocalcaemia (parathyroid glands removed along with the thyroid gland)
2) Horse voice (recurrent laryngeal nerve can be damaged)
3) Hypothyroidsim (obviously!)
4) Risk of local hameorrhage and wound infection too
What are the 3 physiological causes of amenorrhea (no problem causing it)?
1) Pregnancy
2) Lactation
3) Menopause
What could be the cause of secondary amenorrhoea?
1) Ovarian: polycystic ovarian disease, premature ovarian failure
2) Uterine: adhesions in the uterus
3) Pituitary: hypopituitarism, prolactinoma (prolactin secretion suppresses sex hormones)
4) Hypothalamic: excessive exercise, severe weight loss, stress, hypothalamic tumours
5) General endocrine (these are usually associated with menstrual irregularities rather than amenorrhoea): thyroid dysfunction, cushing’s syndrome
