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.