Endocrinology: Adrenal & Thyroid gland and pancreas Flashcards
What are the 3 zones of the adrenal cortex?
- Zona glomerulosa
- Zona Fasiculata
- Zona Reticularis
What hormones are produced from the adrenal cortex and from which area?
- Mineralcorticoid (Aldosterone) Zona Glomerulosa
- Glucocorticoids (Cortisol) - Zona fasciculata
- Adroden precursor (DHEA) Zona reticularis
All hormones produced in the adrenal cortex are made from what compenent?
Cholesterol
Where are all adrenocortical steroids broken down
The liver -> Excreted in urine of as bile
Explain the hypothalamo-pituitary-axis and the control of cortisol section
- CRH released from hypothalamus
- Causes release of ACTH from Ant Pituitary gland
- Acts on Adrenal cortisol to stimulated productions of cortisol (also androgens)
- Follows cicadium rhythm
- Negative feedback of cortisol
What are the effects of cortisol
Gluconeogensis - increase glucose
Catabolic effect - decreases protein stores
Anti-inflammatory effects
Explain the release of aldosterone secretion
1) Key detector of changes of perfusion/electrolyes is the juxtaglomerular appartatus within the glomerulus. The juxaglomerular cells on the afferent ariteriole, produce renin.
Renin converts Angiotensin (liver) -> angiotensin 1
ACE (lungs) converts angiotensin 1 -> angiotensin 2
Angiotensin 2 -> Increaseses aldosterone production, vasoconstriction and increases thirst.
2) High K causes release of aldosterone
What are the effects of aldosterone on the kidney?
Reabsorbtion of Na and K excretion.
Water follows Na passively, increases volume of fluid
What is produced in the adrenal medulla? Name the cells that produce this hormone
Epinephrine & Norepinephrine
Chromafin cells
What are catecholamines (epineprhine, thryoid, melatonin) made from
Tyrosine
How is the output of catecholamines from the adrenal medulla controlled?
What is the half life of carecholamines?
Posterior hypothalamus stimulates the release of acetylcholine form the preganglionic nerve terminals, these depolarise the chromaffin cells.
Very short - 1-2 minutes
Catecholeamines act on 2 broad caterogories of G protein couple receptors what are these?
Alpha-adrenergic -> diverts blood to skeletal muslce from bowel/liver/spleen
Beta adrenergic -> increase HR, stroke volume, BP, mobilisation of gluose, lioplysis
What is the difference between cushing disease and cushing syndrome?
Cushing disease: Excess glucorticoid from ACTH secreting pitutiary tumour
Cushing syndrome: Ectopic ACTH e.g. lung tumor - may not have classic symptoms
What are the clinical features of cushings syndrome
- Moon face
- Weight gain with central obesity
- HTN
- Mental change
- Hirsuitism
- Striae
- ACEne
- Osteoporosis
- +/- other hypopituarism - hypothyroid, hypogondism, low GH
What screening tests for cushings can you consider?
Measure cortisol (24hrs, midnight level)
Low dose dexamethasone test combined with CRH test
Management of cushings
Surgical (pituitary tumour, adrenalectomy)
Medical:
- Prevent hypokalaemia, K sparing diuretic, K supplement
- Cushing syndrome - somatostatin analogues, adrenal steroid inhibitor
What is Conns syndrome?
Primary hypoeraldosteronism
- Excess aldosterone, rentetion of Na and excretion of K, high BP
What are the causes of Conn Syndrome?
Adrenal adenoma
Adrenal gland hyperplasia
Adrenal carcinoma
Who should you suspect Conns Syndrome in?
Unproked hypokalaemia
Persistant hypokalaemia despite K sparing diuretics
Refactory HTN
What is the classic biochemical finding of conns syndrome
Low K
Metabolic alkalosis
Test plama aldosterone/plasma renin ratio (not on antihypertensives)
What are the treatment options for Conns Syndrome
If from a adrenal tumour -> surgical removal
If bilateral renal hyperplasia -> Medications (Spironolactone but has estogen SE; impotence and gynacomastia or Eplerenone; anti-aldosterone)
What is a phaeochromocytoma & where does it arise?
Rare catecholamine secreting tumour of the sympathetic nervous system
90% adrenal
10% sympathetic chain
Excessive catecholmine can lead to what life threatening situations?
Life threatening HTN
Cardiac arrythmia
Investigation for phaeochromocytoma
- Plasma metanephrine
- 24 hour urine catecholamine
- Radioisotope imaging
Managment of phaeochromocytoma
- Surgical removal
- Pre-op Alpha adrenergic and b andrenergic blockade - to help prevent catecholmine storm with GA or operaitive handling
What are the causes of hypoadrenlism?
- Addisions (Primary) due to abrupt cessation of exogenic steroids (>99%)
- Addisons (Primary) due to autoimmunity/infection/haemorrhage/drugs (ketoconazole)
- Seconday - pituitary diease
- Tertiary - Hypothalamic disease
What are the symptoms of addisions disease?
- Weakness
- Weight loss
- Pigmentation
- Anorexia
- Nausea
- Abdo pain
What are classic biochemical features of hypoadrenalism?
Low Na
High K
High Ca
How do you test for hypoadrenalism
ACTH suppression test
Give synthetic ACTH & measure cortisol + ACTH
Primary: High ACTH, low cortisol
Secondary: Low ACTH, low (but slightly increased) cortistol
Acute management of adrenal crisis
A-E approach
IV access with fluid repalcemnt NaCl
Measure +/- replace glucose
100mg hydrocortisone , further 100-200mg over 24 hours
Long term
- 2-3 daily doses hydrocortisone
- Fludrocortisone
- No mineralcorticoid replacment needed
- Some replace DHEA in females
- sick day rules for hydrocortisone
What is congenital adrenal hyperplasia?
Autosome reccessive disoders, enzyme deficient involved in the productions of cortisol or aldosterone. Examples 21-hydroxylase.
What is the clinical presentation of congenital adrenal hyperplasia?
Depends on severity and sex of the child.
- Severe: Salt-wasting at weeks 1-4 (hypotension, low Na, highK, shock)
- Severe famale: Ambigious genitalia at birth
- Mild females: Precocious pubic hair, clitoromegaly, accelerated growth (simple virilising adrenal hyperplasia)
- Milder female: oligomenrrorhia, hirsiutism +/- infertility
- No breast/mensus +/- HTN
- Men have normal genitialia
How to screen for congenital adrenal hyperplasia on bloods
- Electrolytes
- blood sugar
- cortisol
- aldosterone
- 17 hydroxyprogesterone (precursor to 21 hydroxylase)
What hormones does the Thyroid Gland produce which cells?
- Follicular cells - T4 & T3
- C Cells - calcintonin
What suppresses TSH as part of the negative feedback loop?
- Free T3 & T4
- Somatostatin
- Glucocorticoids
- Chronic illness
What percentage of T3 & T4 are bound.
How does peripheral tissue regulate these levels?
T3 1% unbound
T4 0.1%
Peripheral tissues change T3 synthesis, whilst T4 can be converted to T3 by deiodination
How does thyroid hormeones bind to cells & generally what effect does this have
Nuclear transcription factors, receptors in nucleas and regulated gene expression. Increases metabolic rate.
What is the most common cause of hyperthyoid in a young vs and old person
Young: Graves
Old: Toxic multinodular goitre
What features are only seen in Graves disease as supposed to other causes of hyperthyroidism?
Opthalmopathy
Dermopathy
Diffusely enlarged smooth goitre
In subclinical hyperthyroidism - what would you see on bloods
Normal free T4&T3
Suppressed TSH
Described the presentation of radioactive iodone in: Graves, thyroiditis/iodine ingestions, multinodular goitre
Graves: diifusely distributed within entire gland
Thyroiditis/Iodine: poor uptake
Multinodular: multifocal areas of varying activity
What treatment of hyperthyroidism is often used in pregnancy & why?
Thicarbamides - propylthiouracil over carbimazole as crosses placenta and breast milk in smaller amounts
Radioactive iodine is contraindicated in children, pregnancy & breast feeding. Must wait alteast 4 month after radioactive iodine before becoming pregnant.
Antithyroid peroxidases seen in hashimotos disease (form of primary hypothyroidism) is associated with what early pregnancy outcomes?
Infertility
miscarriage
Most common cause of hypothyroidism in developing countries
Iodine insufficiency
How do you treat hypothyroidism, how does this treatment work?
After starting Tx when should you recheck TFT
Levothyroxine - Free T4, can be converted to T3 in peripheral tissues
Treat hypothyroid and subclinical with +ve antithyroid microsome antibodies
Recheck in 6 weeks
Should you routinely test a critically ill person for thyroid function?
No - when crtically, T4 not exchanges to T3 in peripheral levels
Normal/Low TSH, Low T4, Very Low T3
In pregnancy maternal thyriod is modulated by what 3 factors?
- Increasing bHCG (similar to TSH), simulates the thyroid gland -> 1st trimester T4 normal or slightly high, TSH is low. Worse in Hyperemesis or Molar (higher bHCG)
- Increased in excretion of uriary iodine (increased filtration rate) -> thyroid increases in size
- Increased T4 binding globulin in 1st trimester - increased binding T4 - increased total T3&T4 but normal free T3 & T4
Whats likely to happen to thyroid replacement requirements during pregnancy?
Increase
Those already on levothyroxine are liekly going to need 50% increased, needs to be closely monitored.
Those starting Tx need treatment immediately to preven fetal exposure to hypothyroid environement
For women with no previous Hx hypothyroidism, what should happen to thyroid treatment postpartum?
Stop Tx and recheck function 5-6 weeks later
When does the fetus start to develop its own TSH and T4
What are the long term effects of fetal hypothyroidism if left untreated?
Week 10
Profound mental and developmental restriction
- What are the effects of hyperthyroidisim on mensus and fertility.
- Effects on mother during pregnancy
- Effects on the fetus
- Irregular mensus but no effect on fertility
- Premature labour, PET, heart failure
- Neonatal mortality, low birth weight
How does pregnancy effect hyperthyroidism?
Little effect, pregnancy does not make hyperthyroidism harder to control
What is the risk of fetal thyrotoxicosis if mother has Hx Graves. How does it present?
Thyroid stimulating antibodies can cross the placenta, even if mother has been previously treated or is in remission.
Presents in utero with persistant fetal tachycardia, growth failure, increased fetal movements - always consider if any hx of hyperthyroid in mother
During pregnancy how should we adapt how we interpret free T4 vs Total T4
Normal ranges for T4
Multiply total free t4 reference range by 1.5 in 2nd and 3rd trimester
Mother with pre-exsisitng hypothyroidism, when should the T4 dose be increased by?
By weeks 4-6 of pregnancy. Up to 30% increase
When starting levothyroxine in pregnancy, what is the maximum TSH to be maintained in 1st trismester and 2nd/3rd trimester
1st Trimester: <2.5
2nd/3rd: <3
When is fine needle aspiratin requireuired on a solitary thryoid nodule?
- >1cm
- Enlarging
- Cervical lymph nodes palpable
What is postpartum thyroiditis? When and how does it typically present?
5-10% within 1 st year post partum
- Transient Thyrotoxicosis between 2-6monts
- Hypothyroidism between 3-12months
High risk for developing permnant hypothyroidism
What is the risk of developing PP thyroditis if those with antithyroid antibodies?
Risk of reoccuring in furture pregnancy?
90%
25%
Do you need to treat gestational thyrotoxicosis
No - related to elevated bHCG seen in 1st trimester. Will imporve by 20 weeks
More common in multiple pregnancy, molar, famililal gestational thyrotoxicosis
What are the effects of insulin on the liver/adiopse tissue and muscle
- Liver glygogen synthesis
- Adipose - rapid uptake of glucose to be converted to fatty acids
- Muscle - rapid uptake of glucose & amino acids
Insulin causes weight gain
What hormones are produced by the endocrine tissue of the pancreas?
Insulin
Glucagon
Somatostatin
Gastrin
Vasoactive intestinal peptide (VIP)
Pancreatic polypeptide
When is glucogen released, whats its effects?
Low blood glucose/high amino acids/exercise
Opposite effects of insulin mobilising fuels: break down of glycogen, gluconeogensis, release of free fatty acids from adipose cells.
What are the 2 main forms of somatostatin and where are they produced?
Somatostatin 14 (predominant) produced in nervous system
Somatostatin 28 in inestines
Somatostatin 28 is more potent at inhibiting ??
Somatostatin 14 is more ptent at inhibiting?
28: inhibit growth hormone secretion
14: inhibit glucagon release
What are the levels of prediabetes and diabetes for fasting plasma glucose?
> 7.0 diabetes
6.0-7.0 pre-diabetes
OGTT prediabetes and diabetes levels?
>11.1 after 2 hours
7.8-11.2 after 2 hours
HbA1c for Dx of DM
Changes in pregnancy?
6.5% >48mmol/mol
HbA1c should not be used in pregnancy to diagnose DM
What is metabolic syndrome?
T2DM
HTN
Dyslipidaemia (high LDL, low HDL)
What are the effects of metformin?
Who is it contraindicated in?
Impairs release of hepatic glucose
Contrindicated: Poor renal function after radioactive iodine
Explain the peak level and long effects of the following insulins
Rapid acting
Regular/short acting
Intermediate acting
Long acting
Rapid: Few minutes, couple of hours
Regular/short: 30 mins, 3-6 hours
Intermediate: 2-4 hours, 18 hours
Long: 6-10 hours, 24 hours
Main 2 regiemes for type 1
1/2 daily dose as either 1 long acting injection or 2 x intermediate
Remainder short acting before meals
What is the normal starting dose of insulin based on weight for T1DM, whats it often icnreased to?
Starting 0.2-0.4 U/Kg
0.6-0.7 U/kg daily
In a normal pregnancy, why happens to
- fasting plasma glucose
- fasting levels of insulin
- meternal hepatic production of glucose
- insulin sensitivity
- Insulin levels
- fasting plasma glucose is lower (uptake from placenta/fetus)
- fastiing insulin is increased
- maternal hepatic glucose is increased because..
- there is decreased insulin sensitivity
- progressively increases with gestation
In a normal pregnancy (non obese, non diabetic)
- How much fat gain is expected
- Changes to triglyceride concentraion
- Changes to levels of Total cholesterol
- Chanes in LDL and HDL by mid gestation
- 3.5kg
- 2-4 x
- Increases 25-50%
- LDL 50%, HDL 30%
What happens to the fetal islet cells in the pacreas in maternal DM
Hypertrophy, increasing insulin secretion
What % of DM in pregnancy is GDM?
What % pregnacies are effect by GDM?
90%
1-4%
Risk factors for GDM
- High mat age
- Ethnicity
- obesity
- gestational weight gain
- suspected macrosomia/previous macrosomia
- polyhydramnios
- glycosuria
- previous GDM
- Hx DM
- prv stillbirth, neonatal death, congital abnormallity
When is testing of GDM normally perfored. For those with previous GDM
Cut of for OGTT
24-28 weeks, additional testing 16-18 weeks for those previosuly with GDM/
>11.1
Fetal morbity related to DM during pregnancy
- Higher rates of miscarriage, poor control rates of 44%
- Major birth defect 4-8% increases risk -risk CV and neurological anomilies
- Macrosomia 15-45%, unique pattern of overgrowth in central deposition and intrascapular area - realted birth injuries
- Polycythaemia 5-10%
- Severe hypoglycaemia 5 x increased
- growth restriction (T1DM with vasculopathies)
- Increased lifetime risk of imparied glucose tolerace, 20% by aged 10-16 years
What link is there between obesity and subfertility
Obestity - hyperinsulinaemia and hyperandrogaemic state leading to oligo/amennorhoea, risk of anovulatory fertility.
Weight loss is essential
Women who are obese are more likely to suffer from:
- VTE
- GDM
- PIH/PET
- Proteinuia >20 weeks
- stillbirth/intrauterine death
- Preterm labour, miscarriage, fetal chormosomal abnormality, macrosomia
- dysfunctional labour
- CS perioperative morbidity
- PPH
