Endocrinology Revision Flashcards
What is the most common drug causing gynaecomastia?
Spironolactone
How can goserelin cause gynaecomastia?
GnRH agonist
In normal physiology, the pulsatile release of GnRH stimulates testosterone production.
When goserelin is given long-term in a non-pulsatile manner, this disrupts the endogenous feedback loops controlling testosterone production, and results in hypoandrogenism.
This in turn causes the development of gynaecomastia.
What is Conn’s syndrome?
1ary hyperaldosteronism
Most common cause of 1ary hyperaldosteronism?
Bilateral idiopathic adrenal hyperplasia
Features of 1ary hyperaldosteronism?
1) HTN
2) Hypokalaemia
3) Metabolic alkalosis
How can hypokalaemia present?
Muscle weakness
1st line investigation in suspected Conn’s?
Plasma aldosterone/renin ratio
What will a plasma aldosterone/renin ratio show in Conn’s?
HIGH aldosterone levels alongside LOW renin levels (negative feedback due to sodium retention from aldosterone)
What is next investigation following plasma aldosterone/renin ratio in Conn’s?
High resolution CT & adrenal vein sampling
These are used to differentiate between unilateral and bilateral sources of aldosterone excess
Mx of adrenal adenoma causing Conn;s?
surgery (laparoscopic adrenalectomy)
Mx of bilateral adrenocortical hyperplasia causing Conn’s?
Aldosterone antagonist e.g. spironolactone
What is seen in sick euthyroid?
TSH low or normal
T3 & T4 low
What is the most important modifiable risk factor for the development of thyroid eye disease?
Smoking
What is subacute thyroiditis (De Quervain’s thyroiditis)?
Typically presents with hyperthyroidism.
Thought to follow viral infection.
What are the 4 phases of hyperthyroidism?
phase 1 (lasts 3-6 weeks): hyperthyroidism, painful goitre, raised ESR
phase 2 (1-3 weeks): euthyroid
phase 3 (weeks - months): hypothyroidism
phase 4: thyroid structure and function goes back to normal
What is seen on thyroid scintigraphy in De Quervain’s thyroiditis?
globally reduced uptake of iodine-131
Does Cushing’s cause a metabolic acidosis or alkalosis?
Alkalosis –> bicarbonate resorption is increased in the tubules with potassium depletion
Mechanism of labetalol?
Both alpha AND beta blocking qualities
Definitive mx of primary hyperparathyroidism?
total parathyroidectomy (NOT subtotal)
How often must insulin-dependent diabetics check their blood glucose whilst driving?
Every 2 hours
1st line insulin regime for newly diagnosed adults with type 1 diabetes?
basal-bolus using twice-daily insulin detemir
What conversion is impaired in CAH caused by 21-hydroxylase deficiency?
Impairs the conversion of 17-hydroxyprogesterone to 11-deoxycortisol, leading to cortisol deficiency and excess androgen production
Therefore there will be increased plasma 17-hydroxyprogesterone levels.
What is required for both PTH secretion & its action on target tissues?
Magnesium
How can hypomagnesaemia affect calcium?
Hypomagnesaemia may both cause hypocalcaemia and render patients unresponsive to treatment with calcium and vitamin D supplementation.
1st line in pregnant woman who develop hyperthyroidism in the first trimester?
Prophylthiouracil
Due to lower risk of foetal malformation
Where is ADH produced & stored?
Produced - hypothalamus
Stored - posterior pituitary
What type of diabetes insipidus can hypercalcaemia cause?
Nephrogenic
What type of diabetes insipidus can lithium cause?
Nephrogenic
What type of diabetes insipidus can hypokalaemia cause?
Nephrogenic
Give some causes of cranial diabetes insipidus
1) Idiopathic
2) Brain tumours
3) Brain surgery
4) Brain infections e.g. meningitis, encephalitis
5) Genetic mutations in the ADH gene (autosomal dominant inheritance)
6) Wolfram syndrome
What is Wolfram syndrome? (4)
A genetic condition causing:
1) cranial diabetes insipidus
2) optic atrophy
3) deafness
4) diabetes mellitus
What needs to be monitored during treatment of cranial diabetes insipidus with desmopressin?
Sodium –> increased risk of hyponatraemia (due to increased water retention and dilution of blood).
Define subclinical hyperthyroidism
Describe T3/T4 levles and TSH levels
Low TSH
Normal T3/T4
What abs are seen in grave’s disease?
TSH receptor autoantibodies (stimulate TSH receptors)
Does Grave’s disease cause 1ary or 2ary hyperthyroidism
1ary
What is a toxic multinodular goitre?
Nodules develop on the thyroid gland, which are unregulated by the thyroid axis and continuously produce excessive thyroid hormones.
What are 4 features specific to Grave’s disease?
1) Grave’s eye disease, including exopthalmos
2) Pretibial myoxedema
3) Thyroid acropachy (hand swelling and finger clubbing)
4) Diffuse goitre (without nodules)
Describe the goitre in Grave’s?
Diffuse, without nodules
What causes pretibial myoxedema?
Deposits of glycosaminoglycans under the skin on the anterior aspect of the leg.
Gives the skin a discoloured, waxy, oedematous appearance over this area.
What are the 4 main causes of hyperthyroidism?
1) Grave’s
2) TMN
3) Solitary toxic thyroid nodule
4) Thyroiditis
How does thyroiditis affect thyroid levels?
Often causes an initial period of hyperthyroidism, followed by hypothyroidism.
What are the 4 main causes of thyroiditis?
1) De Quervain’s thyroiditis
2) Hashimoto’s thyroiditis
3) Postpartum thyroiditis
4) Drug-induced thyroiditis
What drugs can cause hyperthyroidism?
Amiodarone
What are solitary toxic thyroid nodules normally?
Benign adenomas
Management of a solitary thyroid nodule?
Surgical removal
What is De Quervain’s thyroiditis also known as?
Subacute thyroiditis
What happens in De Quervain’s thyroiditis?
It is a condition causing temporary inflammation of the thyroid gland.
There are 3 phases:
1) Thyrotoxicosis
2) Hypothyroidism
3) Return to normal
Management of De Quervain’s thyroiditis?
It is a self-limiting condition, and supportive treatment is usually all that is necessary. This may involve:
1) NSAIDs for symptoms of pain and inflammation
2) Beta blockers for the symptoms of hyperthyroidism
3) Levothyroxine for the symptoms of hypothyroidism
What is a thyroid storm (thyrotoxic crisis)?
What are the 3 key features?
A rare & severe presentation of hyperthyroidism:
1) fever
2) tachycardia
3) delirium
What are 2 key potential side effects of carbimazole?
1) Acute pancreatitis
2) Agranulocytosis
In your exams, if you see a patient with a sore throat on carbimazole or propylthiouracil, what should you consider?
Agranulocytosis –> get urgent FBC
1st & 2nd line mx of hyperthyroidism?
1st –> carbimazole
2nd –> propylthiouracil
What are the strict rules surrouning treatment with radioactive iodine?
1) Women must not be pregnant or breastfeeding and must not get pregnant within 6 months of treatment
2) Men must not father children within 4 months of treatment
3) Limit contact with people after the dose, particularly children and pregnant women
Mechanism of carbimazole?
Anti-thyroid agent:
Converted to its active form of methimazole which then inhibits thyroid peroxidase (TPO)
What is the role of TPO?
TPO normally catalyses the iodination of tyrosine residues in thyroglobulin and the oxidative coupling of iodinated tyrosine.
Contraindications of carbimazole?
1) pregnancy
2) breastfeeding
3) severe blood disorders
What is the most common cause of hypothyroidism in the developed world?
Hashimoto’s
What is the most common cause of hypothyroidism worldwide?
Iodine deficiency
What is Hashimoto’s thyroiditis?
Autoimmune condition
Anti-TPO & anti-Tg antibodies
How can lithium affect the thyroid?
Can cause hypothyroidism
What is Sheehan’s syndrome?
Where anterior pituitary is damaged due to avascular necrosis after significant blood loss.
E.g. post major PPH
Which causes of hypothyrodism can cause a goitre?
1) Iodine deficiency
2) Hashimoto’s thyroiditis can initially cause a goitre, after which there is atrophy (wasting) of the thyroid gland.
What is levothyroxine?
Synthetic version of T4
Is T3 or T4 active?
T3 is active version
T4 is inactive version
How is the dose of levothyroxine titrated?
The dose is titrated based on the TSH level, initially every 4 weeks.
What 2 electrolyte abnormalities can cause nephrogenic diabetes insipidus?
1) hypercalcaemia
2) hypokalaemia
Infection with what bacteria is a CF-specific contraindication to lung transplantation?
Burkholderia cepacia
Give some causes of acanthosis nigricans
1) T2DM
2) PCOS
3) Hypothyroidism
4) COCP
5) Gastric cancer
6) Obesity
7) Acromegaly
8) Cushing’s
In type 1 diabetes, when is adding metformin considered on top of insulin therapy?
If BMI ≥25
What vaccinations should be offered to patients with confirmed heart failure?
1) Annual influenza
2) Once off pnuemococcal
Hashimoto’s thyroiditis is associated with the development of what cancer?
MALT lymphoma
What fasting blood glucose indicates T2D?
≥7.0 mmol/l
What class of diabetes medication can cause SIADH?
Sulfonylureas
Patients with type I diabetes and a BMI > 25 should be considered for what in addition to insulin?
Metformin
What is impact on driving of having TWO hypoglycaemic episodes requiring treatment?
Must surrender their license - contact DVLA and stop driving immediately
What is Trousseau’s sign a result of?
Hypocalcaemia
What is the most common type of thyroid cancer?
Papillary (70%)
Who is papillary thyroid cancer often seen in?
Young females
What type of thyroid cancer secretes calcitonin?
Medullary
What does increased homogenous uptake on a radioactive iodine uptake test suggest?
Grave’s disease
What is subacute thyroiditis (also known as De Quervain’s thyroiditis) thought to occur after?
Viral infection
What 2 tablets can reduce the absorption of levothyroxine?
1) iron
2) calcium carbonate tablets
Take these & levothyroxine at least 4 hours apart.
NICE CKS have published guidance on the management of patients with subclinical hypothyroidism and recommend a ‘watch and wait’ approach in patients over the age of what?
80 y/o
What is a pheochromocytoma?
A rare catecholamine secreting tumour.
1st line investigation in a phaeochromocytoma?
24 hr urinary collection of metanephrines (sensitivity 97%*)
When should subclinical hypothyroidism be treated?
If TSH levels are >10 mU/L on 2 separate occasions 3 months apart
How is hydrocortisone dose given in Addison’s?
The hydrocortisone dose is split with the majority given in the first half of the day
How can steroids affect sleep?
Can cause insomnia
What is an impaired fasting glucose?
6.1-6.9 mmol/l
Which type of diabetes med can cause necrotising fasciitis of the genitalia or perineum (Fournier’s Gangrene)?
SGLT-2 inhibitors
How can haemodialysis affect HbA1c?
Can give a falsely low HbA1c
Mx of phaeochromocytoma?
Surgery
Before surgery, the patient must be stabilised with medical mx:
1) alpha-blocker (e.g. phenoxybenzamine), given before a
2) beta-blocker (e.g. propranolol)
Patients with Addison’s should be given a what in case of adrenal crises?
IM hydrocortisone injection kit
What is thyroid eye disease (AKA Grave’s ophthalmopathy)
Autoimmune disorder characterised by the infiltration of immune cells and deposition of glycosaminoglycans within the extraocular muscles and orbital connective tissues.
Results in inflammation, oedema, and fibrosis.
What is the most important modifiable risk factor for the development of thyroid eye disease?
Smoking
What treatment may increase the inflammatory symptoms seen in thyroid eye disease?
Radioiodine treatment (prednisolone may help reduce risk)
Features of thyroid eye disease?
- exophthalmos/proptosis
- conjunctival oedema
- optic disc swelling
- ophthalmoplegia
- inability to close the eyelids may lead to sore, dry eyes (can be at risk of exposure keratopathy)
Mx of thyroid eye disease?
- topical lubricants
- steroids
- radiotherapy
- surgery
For patients with established thyroid eye disease, what signs & symptoms should indicate the need for urgent review by an ophthalmologist?
- unexplained deterioration in vision
- awareness of change in intensity or quality of colour vision in one or both eyes
- history of eye suddenly ‘popping out’ (globe subluxation)
- obvious corneal opacity
- cornea still visible when the eyelids are closed
- disc swelling
What is the most common cause of 2ary HTN?
Primary hyperaldosteronism
How can a non-functioning pituitary adenoma cause raised prolactin levels?
The elevated prolactin level is caused by stalk effect or compression of the pituitary stalk by the adenoma.
This compression disrupts dopamine transport from hypothalamus to anterior pituitary lactotroph cells.
Dopamine usually inhibits prolactin release; therefore, its disruption leads to increased prolactin levels.
What is used for the diagnosis of T1D in children?
Random plasma glucose
