Endocrine Flashcards
hyperthyroidism definition
over-production of the thyroid hormones, triiodothyronine (T3) and thyroxine (T4), by the thyroid gland
thyrotoxicosis definition
refers to effects of an abnormal and excessive quantity of thyroid hormones in the body
primary hyperthyroidism
due to thyroid pathology
thyroid is behaving abnormally and producing excessive thyroid hormone
secondary hyperthyroidism
- pathology in the hypothalamus or pituitary
- pituitary gland produces too much thyroid-stimulating hormone, stimulating the thyroid gland to produce excessive thyroid hormones.
subclinical hyperthyroidism
- thyroid hormones (T3 and T4) are normal and thyroid-stimulating hormone (TSH) is suppressed (low)
what is grave’s disease?
- an autoimmune condition where TSH receptor antibodies cause primary hyperthyroidism
- These TSH receptor antibodies stimulate TSH receptors on the thyroid
- most common cause of hyperthyroidism
what is Toxic multinodular goitre?
- a condition where nodules develop on the thyroid gland, which are unregulated by the thyroid axis and continuously produce excessive thyroid hormones
- It is most common in patients over 50 years.
which hormones are released by anterior pituitary
FLAT PEG
- FSH
- LH
- Adrenocorticotropic hormone (ACTH)
- Thyroid-stimulating hormone (TSH)
- Prolactin
- Growth hormone (GH)
briefly outline the thyroid axis?
- hypothalamus releases thyrotropin-releasing hormone (TRH)
- TRH stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH)
- TSH stimulates the thyroid gland to release triiodothyronine (T3) and thyroxine (T4)
NB hypothalamus and anterior pituitary respond to T3 and T4 by suppressing the release of TRH and TSH = negative feedback
which hormones are release by posterior pituitary?
Oxytocin
Antidiuretic hormone (ADH)
briefly summarise the growth hormone axis
- hypothalamus produces growth hormone-releasing hormone (GHRH)
- GHRH stimulates the anterior pituitary to release growth hormone (GH)
- Growth hormone stimulates the release of insulin-like growth factor 1 (IGF-1) from the liver
what hormone inhibits growth hormone release from anterior pituitary?
somatostatin
what does insulin-like growth factor do?
- stimulates fat breakdown
- releases glucose from liver
- cell division
- protein synthesis
- increased bone density
causes of hyperthyroidism?
G – Graves’ disease
I – Inflammation (thyroiditis)
S – Solitary toxic thyroid nodule - usually benign adenoma
T – Toxic multinodular goitre
causes of thyroiditis (gland inflammation that causes hyperthyroid then hypothyroid) ?
- DeQuervain’s - transient inflammation of thyroid after viral infection
- Hashimoto’s
- Post-partum
- Drug-induced - amiodarone, iodine, lithium
Hyperthyroidism Px
Anxiety and irritability
Sweating and heat intolerance
Tachycardia
Weight loss
Fatigue
Insomnia
Frequent loose stools
Sexual dysfunction
Brisk reflexes on examination
Graves specific Px ?
Diffuse goitre (without nodules)
Graves’ eye disease, including exophthalmos (eye bulging)
Pretibial myxoedema
Thyroid acropachy (hand swelling and finger clubbing)
Hyperthyroidism Ix
- TFTs - high T3/4, TSH low (high in 2ndary)
- Thyroid ABs - TSHR-Ab, TPO-Ab, TgAb
- CRP / ESR - thyroiditis
- baseline FBC, U/E
- US thyroid - if lump
- thyroid isotope scan
Hyperthyroidism Mx
1st line = carbimazole (start high, titrate down, block and replace by adding lego)
2nd line = propylthiouracil
- radioactive iodine
- subtotal / total thyroidectomy
beta blockers can be used for symptom control
possible side effects of carbimazole?
risk of:
- neutropenia
- agranulocytosis
- congenital malformations
What is a thyrotoxic crisis (aka thyroid storm) and how do you manage it?
- rapid T4 increase / release
- eg stress, infection, surgery, stopping anti-thyroid drugs
Px
- high temp, tachy, restless, delirium, coma, death
Mx
- IV fluids, corticosteroids, BBs, carbimazole / propylthiouracil
- potassium iodide
what is hypothyroidism? define primary and secondary?
Low TH - T3/4
Primary - thyroid gland disease - T3/4 low, TSH high
Secondary - disease of hypothalamus / pituitary - T3/4 low, TSH low
Causes of primary hypothyroidism
Primary:
1. Hashimoto’s - autoimmune inflammation
2. iodine deficiency
3. hyperthyroidism Tx
4. lithium
Causes of secondary hypothyroidism
Secondary:
1. Tumours (e.g., pituitary adenomas)
2. Surgery to the pituitary
3. Radiotherapy
4. Sheehan’s syndrome (where major post-partum haemorrhage causes avascular necrosis of the pituitary gland)
5. Trauma
what antibodies are associated with Hashimoto’s?
- anti-thyroid peroxidase (anti-TPO) antibodies
- anti-thyroglobulin (anti-Tg) antibodies
what is Sheehan’s syndrome?
major post-partum haemorrhage causes avascular necrosis of the pituitary gland leading to hypopituitarism
Hypothyroidism Px
Weight gain
Fatigue
Dry skin
Coarse hair and hair loss
Fluid retention (including oedema, pleural effusions and ascites)
Heavy or irregular periods
Constipation
Hypothyroidism Ix
- TFTs
- thyroid ABs - anti-TPO, anti-Tg
- FBC - anaemia
Hypothyroidism Mx
- levothyroxine
Myoxedema coma
- severe hypothyroidism
Px
- confusion, coma, hypothermia, hypoglycaemia, hyponatraemia
Mx
- T3/4 replacement (T3 causes arrhythmias)
- IV glucose
- hydrocortisone if needed
- fluids / supportive care
describe the renin-angiotensin aldosterone system
1) low bp sensed by juxtaglomerular cells in afferent arterioles of kidneys stimulating renin secretion
2) renin converts angiotensinogen (from liver) to angiotensin 1
3) angiotensin 1 converted to angiotensin 2 by ACE (released by lungs)
4) angiotensin 2 stimlates aldosterone secretion from adrenals
what are the actions of aldosterone?
- increase Na reabsorption
- increased K secretion from distal tubules
adrenal axis: mechanism of glucocorticoid release?
stress and time of day (AM) stimulate hypothalamus to secrete corticotropin-releasing hormone (CRH)
CRH stimulates anterior pituitary to secrete adrenocorticotrophic hormone (ACTH)
ACTH stimulates adrenals to secrete glucocorticoids (cortisol, cortisone, corticosterone)
6 actions of cortisol?
1 - stimulates metabolic rate
2 - increases alertness
3- increases sodium and water reabsorption
4 - increases blood sugar levels
5 - inhibits immune system
6 - inhibits protein synthesis / bone formation
What is cushing’s syndrome ?
refers to signs and symptoms of prolonged high levels of glucocorticoids in the body.
Cushing’s disease?
refers to a pituitary adenoma secreting excessive adrenocorticotropic hormone (ACTH), which stimulates excessive cortisol release from the adrenal glands
Causes of cushing’s syndrome ?
C – Cushing’s disease (a pituitary adenoma releasing excessive ACTH)
A – Adrenal adenoma (an adrenal tumour secreting excess cortisol)
P – Paraneoplastic syndrome
E – Exogenous steroids (patients taking long-term corticosteroids)
Cushing’s features?
- Round face (known as a “moon face”)
- Central obesity
- Abdominal striae (stretch marks)
- Enlarged fat pad on the upper back (known as a “buffalo hump”)
- Proximal limb muscle wasting (with difficulty standing from a sitting position without using their arms)
- Male pattern facial hair in women (hirsutism)
- Easy bruising and poor skin healing
- Hyperpigmentation of the skin in patients with Cushing’s disease (due to high ACTH levels)
may also see: HTN, T2DM, osteoporosis, dyslipidaemia, mental health problems
Cushing’s Ix
- low dose dexamethasone suppression test to confirm cushing’s
- high dose dexamethasone suppression test to determine cause of Cushing’s
- FBCs and U&Es
- MRI/ CT TAP
what are the low/high dose dexamethasone suppresion tests?
low dose
- give 1mg dex at night and measure ACTH and cortisol in the AM. dex will normally suppress cortisol so failure to suppress suggests Cushing’s
high dose
- give 8mg dex at night and measure ACTH and cortisol in the AM. high dos is enough to suppress cortisol caused by pituitary adenoma (cushing’s disease) but not if due to adrenal adenoma / ectopic ACTH
Cushing’s Mx
- stop steroids
- Cushing’s - transsphenoidal resection of adenoma
- Adrenal adenoma - adrenalectomy
- adrenal carcinoma - surgery / radio / mitotane
- ectopic ACTH - surgery / metyrapone / ketoconazole
Nelson’s syndrome
development of an ACTH-producing pituitary tumour after the surgical removal of both adrenal glands due to a lack of cortisol and negative feedback. It causes skin pigmentation (high ACTH), bitemporal hemianopia and a lack of other pituitary hormones
Hyperaldosteronism: primary versus secondary
excess aldosterone
Primary
- adrenals producing too much aldosterone, renin low due to high BP
Secondary
- high renin levels leading to high aldosterone
Causes of hyperaldosteronism: primary and secondary
Primary
- Adrenal adenoma - Conn’s syndrome
- bl adrenocortical hyperplasia (more common)
Secondary
- reduced renal perfusion e:g
- renal artery stenosis
- HF
- liver cirrhosis / ascites
Hyperaldosteronism Px
- asym
- HTN, headaches, flushing
- metabolic alkalosis - H secretion
- hypokalaemia - weakness, cramps, paraesthesia, polyuria, polydipsia, constipation, arrhythmias
Hyperaldosteronism Ix
1) aldosterone-to-renin ratio (ARR)
2) Raised blood pressure (hypertension)
3) Low potassium (hypokalaemia)
4) Blood gas analysis (alkalosis)
5) CT / MRI
6) renal artery imaging - eg doppler, angiography
7) adrenal vein sampling - which adrenal gland is producing more aldosterone
aldosterone-to-renin ratio (ARR) results in primary versus secondary hyperaldosteronism
High aldosterone and low renin indicate primary hyperaldosteronism
High aldosterone and high renin indicate secondary hyperaldosteronism
Hyperaldosteronism Mx
- oral spironolactone or eplerenone
Surgical removal of the adrenal adenoma
Percutaneous renal artery angioplasty via the femoral artery to treat renal artery stenosis
adrenal insufficiency defintion
underproduction of adrenal cortex hormones - mineralocorticoids (aldosterone) and glucocorticoids (cortisol)
primary adrenal insufficiency: pathology site and causes?
damage to adrenal glands means not enough hormones are produced
causes: Addison’s, infection, surgery, malignancy
secondary adrenal insufficiency: pathology site and causes?
damage to pituitary (so not enough ACTH)
causes: pituitary adenoma, Sheehan’s syndrome, pituitary injury (infection/surgery/malignancy)
tertiary adrenal insufficiency: pathology site and causes
inadequate CRH release from hypothalamus
causes:
cessation of long term steroid use (>3m)
what is Sheehan’s?
major post-partum haemorrhage causes avascular necrosis of the pituitary gland
Adrenal insufficiency presentation?
- tanned, toned, tired, tearful
- fatigue, muscle weakness, cramps, dizziness, fainting, thirst, wt loss, abdo pain, N+V, depression, reduced libido, vitiligo, bronze hyperpigmentation, postural hypotension
what do you see bronze pigmentation in adrenal insufficiency?
ACTH stimulates melanocytes to produce melanin
Adrenal insufficiency Ix
1) bloods
2) short synacthan test
3) ACTH test
4) adrenal autoantibodies
5) CT/MRI of adrenals or MRI pituitary
autoantibodies that may be present in autoimmune adrenal insufficiency?
Adrenal cortex antibodies
21-hydroxylase antibodies
biochemical findings you might see in someone with adrenal insufficiency?
Hyponatraemia (low sodium)
Hyperkalaemia (high potassium)
Hypoglycaemia (low glucose)
Raised creatinine and urea due to dehydration
Hypercalcaemia (high calcium)
what is the short synacthan test?
- give dose of synthetic ACTH
- check blood cortisol before and 30 mins after dose
- cortisol level should double
failure to double suggests Addison’s or significant adrenal atrophy due to secondary insufficiency
Adrenal insufficiency Mx
- hydrocortisone (double when ill) = glucocorticoid replacing cortisol
- fludrocortisone = mineralocorticoid replacing aldosterone
- steroid card, ID tag, IM hydrocortisone
Adrenal crisis
- acute severe adrenal insufficiency - eg infection, trauma
Px
- low GCS, hypotension, low BMs, low Na, high K
Mx
- IM/IV hydrocortisone (100mg stat), IV fluids, IV dextrose
Acromegaly
- excess GH in adults due to pituitary adenoma (most common) or ectopic production of hormones involved in growth hormone axis (GH/ GHRH) (usually cancer e.g. lung/pancreas)
what visual field defect might be seen with a pituitary tumour?
bitemporal hemianopia
Acromegaly Px
Excess growth hormone causes tissue growth:
- Prominent forehead and brow (frontal bossing)
- Coarse, sweaty skin
- Large nose
- Large tongue (macroglossia)
- Large hands and feet
- Large protruding jaw (prognathism)
Additional features include:
- headaches
- Hypertrophic heart
- Hypertension
- Type 2 diabetes
- Carpal tunnel syndrome
- Arthritis
- Colorectal cancer
Acromegaly Ix
- IGF-1 = raised
- growth hormone suppression test = 75g glucose drink with growth hormone tested at baseline and 2 hours following the drink.Glucose should suppress GH level. Failure to suppress GH suggest acromegaly.
- MRI pituitary
Acromegaly Mx
- surgical = transsphenoidal resection of adenoma
- medical = IM octreotide (somatostatin analogue)
- oral cabergoline, bromocriptine (dopamine agonist)
- SC pegvisomant (GH receptor antagonist)
growth hormone deficiency: Px, Ix and Mx
Px = small physical features, low energy levels, short stature
Ix = low IGF-1
Mx = daily injections of recombinant human growth hormone
T1DM
Autoimmune destruction of beta cells in pancreas leading to lack of insulin production and a high blood glucose
T1DM Px
- DKA
- polyuria
- polydipsia
- wt loss
ideal blood glucose ?
4.4 – 6.1 mmol/L.
where is insulin produced?
beta cells in the Islets of Langerhans in the pancreas
how does insulin work?
insulin causes:
- cells to take up glucose from blood
- prompt muscle/liver cells to absorb glucose and store it a glycogen (glycogenesis)
where is glucagon produced?
alpha cells in the Islets of Langerhans in the pancreas
how does glucagon work?
- released in response to low blood glucose / stress
- prompts liver to breakdown glycogen to release as glucose = glycogenolysis
- prompts liver to convert fat/protein into glucose = gluconeogenesis
T1DM Ix
- usually clinical
- urine dip for glucose and ketones
- fasting glucose and random glucose
- ? c-peptides - not routine
- ? autoantibodies to distinguish T1 and T2
fasting and random blood glucose thresholds in T1DM
if symptomatic:
fasting glucose greater than or equal to 7.0 mmol/l
random glucose greater than or equal to 11.1 mmol/l (or after 75g oral glucose tolerance test
asymptomatic? as above but on 2 separate occasions
T1DM Mx
- Subcutaneous insulin
- Monitoring dietary carbohydrate intake
- Monitoring blood sugar levels upon waking, at each meal and before bed
- Monitoring for and managing complications, both short and long term
S/C insulin
- ideal is basal-bolus regime
T1DM: what is a basal bolus regimen
- Background, long-acting insulin injected once a day
- Short-acting insulin injected 30 minutes before consuming carbohydrates (e.g., at meals)
T1DM: what is an insulin pump?
pumps that continuously infuse insulin at different rates to control blood sugar levels. They are an alternative to basal-bolus regimes
T1DM sick day rules
- Don’t stop insulin
- Check BMs more frequently
- Consider checking ketones
- Maintain normal meal pattern if possible - carb drinks if necessary
- Drink plenty fluids
T1DM complications: macrovascular + acute complications
- atherosclerosis
- stroke
- IHD
- PVD
Acute
- DKA, HHS, hypos
T1DM complications: microvascular
- diabetic retinopathy
- nephropathy
- neuropathy
- infections (UTI, pneumonia, skin)
insulin adverse effects?
- hypos
- lipodystrophy
- weight gain
T2DM - pathophysiology
increased insulin resistance and decreased production, leading to persistent hyperglycaemia
T2DM risk factors
- non-modifiable - older age, Black / South Asian, FHx
- modifiable - obesity, sedentary lifestyle, high sugar die
T2DM Px
- asym
- fatigue
- polyuria, polydipsia
- wt loss
- opportunistic infections - eg oral thrush
- slow wound healing
- acanthosis nigricans
what HbA1C suggests pre-diabetes?
HbA1c of 42 – 47 mmol/mol indicates pre-diabetes
T2DM diagnosis
HbA1C >48 mmol (6.5%)
[asymptomatic? need two positive tests. symptomatic? 1 positive test]
glucose cut of values for diabetes mellitus Dx [fasting, random, OGTT]
Serum blood glucose
- fasting >7, IGT 6.1-6.9
- random >11.1, IGT 7.8-11
OGTT
- >11.1 2hrs after 75g glucose - diagnostic
T2DM: HbA1C treatment targets
48 mmol/mol for new type 2 diabetics
53 mmol/mol for patients requiring more than one antidiabetic medication
T2DM Mx - lifestyle
lifestyle:
- Low-glycaemic-index, high-fibre diet
- exercise
- weight loss
- manage complications e.g. HTN
T2DM Mx - medical - 4 stages
1st line = metformin [ + SGLT-2 if cardiovascular disease or HF ]
2nd line = add sulfonylurea / pioglitazone / DPP4 inhibitor / SGLT-2 inhibitor
3rd line = triple therapy [metformin + 2 of the 2nd line drugs] or insulin therapy
4th line (triple therapy failure and patient BMI >35) = GLP-1