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PassMed > Endocrinology > Flashcards

Endocrinology Flashcards

1
Q

Where is the site of action of antidiuretic hormone (ADH)?

A

Collecting ducts: stimulates water reabsorption by inducing expression of aquaporin 2 channels

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2
Q

How can lithium use cause nephrogenic diabetes insipidus?

A

The kidneys cannot respond adequately to antidiuretic hormone (ADH) as lithium inhibits the expression of aquaporin-2 channels in the renal collecting duct rather than the distal convoluted tubule

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3
Q

When does central diabetes insipidus occur?

A

Damage to the posterior pituitary gland: insufficient production and release of ADH

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4
Q

Addison’s disease signs and symptoms

A

result of low aldosterone & low cortisol:

  • lethargy, weakness, anorexia, nausea & vomiting, weight loss, ‘salt-craving’
  • hyperpigmentation (especially palmar creases), vitiligo, loss of pubic hair in women, hypotension, hypoglycaemia
  • hyponatraemia and hyperkalaemia
  • crisis: collapse, shock, pyrexia
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5
Q

Most common cause of adrenal insufficiency

A

Addison’s disease (primary adrenal insufficiency) = autoimmune destruction of the adrenal glands
- often seen with other autoimmune diseases such as diabetes type 1

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6
Q

Congenital adrenal hyperplasia

A

Enzyme deficiency e.g. 21 hydroxylase deficiency = Low production of cortisol = Compensatory hyperplasia

Most commonly due to 21-hydroxylase deficiency

Features:
virilisation (making more masculine) of female genitalia
60-70% of patients have a salt-losing crisis at 1-3 wks of age

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7
Q

Tertiary Hyperparathyroidism

A

High Ca2+, Inappropriately elevated PTH, Low Phosphate

Ongoing hyperplasia of the parathyroid glands after correction of underlying renal disorder, hyperplasia of all 4 glands is usually the cause

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8
Q

Primary Hyperparathyroidism

A

Elevated Ca2+, Elevated PTH, Low Phosphate

Most cases due to solitary adenoma (80%)

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9
Q

Secondary Hyperparathyroidism

A

Low Ca2+, Appropriately elevated PTH, Elevated Phosphate

Parathyroid gland hyperplasia occurs as a result of low calcium, almost always in a setting of chronic renal failure

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10
Q

Example of a steroid with very high glucocorticoid activity and minimal mineralocorticoid activity

A

Dexamethasone

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11
Q

What does the adrenal medulla secrete?

A

Catecholamines (adrenaline and noradrenaline)

Test for phaeochromocytoma: urinary free adrenaline

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12
Q

Where is cortisol produced?

A

The zona fasciculata of the adrenal cortex
Test for Cushing’s disease (high cortisol): 24-hour urinary free cortisol
Test for Addison’s disease (low cortisol): short synacthen test (ACTH injection then measure cortisol)

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13
Q

Where is aldosterone produced?

A

Zona glomerulosa of the adrenal cortex

Test for Conn’s disease: aldosterone-renin ratio

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14
Q

Where are androgens produced?

A

Zona reticularis of the adrenal cortex

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15
Q

Where are glucocorticoids produced?

A

Zona fasciculata of the adrenal cortex

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16
Q

Example of a steroid with minimal glucocorticoid activity and very high mineralocorticoid activity

A

Fludrocortisone

Side effects of mineralocorticoid activity: fluid retention,

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17
Q

What do mineralocorticoid steroids mimic?

A

Aldosterone = regulation of sodium and water retention in response to low blood pressure.

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18
Q

What do glucocorticoid steroids mimic?

A

Cortisol = carbohydrate metabolism and the stress response.

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19
Q

Side effect of steroids with high mineralocorticoid activity?

A

Fluid retention, hypertension

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20
Q

Side effect of steroids with high glucocorticoid activity?

A

Depression, hyperglycaemia, osteoporosis and peptic ulceration
= need to do four times daily capillary blood glucose in patients with diabetes on high glucocorticoid steroids

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21
Q

Features of Addisonian/Adrenal crisis

A

Fatigue, syncope, hyperpigmentation, hypotension, hypoglycaemia, hyponatraemia and very low cortisol.

22
Q

Which cells release renin

A

Juxtaglomerular cells

23
Q

Which cells produce ACE

A

Pulmonary endothelium

24
Q

Lipodystrophy

A

Insulin can cause small subcutaneous lumps at injection sites (can be prevented by rotating the injection site)

25
Q

HCG secreting seminoma

A

Type of seminoma and a germ cell tumour.
Human chorionic gonadotropin (HCG) = this hormone can cause oestrogen production out of proportion with normal androgens, resulting in gynaecomastia in males

26
Q

Octreotide

A

Prescribed for Acromegaly: Somatostatin analogue

= Somatostatin directly inhibits the release of growth hormone

27
Q

Hypospadias

A

Birth defect in boys in which the opening of the urethra is not located at the tip of the penis
Cryptorchidism (undescended testes) is present in around 10% of patients with hypospadias

28
Q

Thiazolidinediones (e.g. pioglitazone)

A

Activate the peroxisome proliferator-activated receptor gamma (PPAR gamma) and modulate the transcription of genes involved in glucose and lipid metabolism

= overall increases insulin sensitivity and decreases hepatic glucose production

!! contraindicated in patients with heart failure.

29
Q

Sulphonylureas (e.g. gliclazide)

A

Bind to KATP channels on pancreatic beta cells to stimulate insulin release

! weight gain
! hypoglycaemia risk

30
Q

Sodium-glucose co-transporter-2 (SGLT2) inhibitors

A

(also known as the ‘flozins’)
Inhibit renal glucose reabsorption = promote glycosuria

!! increase the frequency of urinary tract infections

31
Q

Dipeptidyl peptidase-4 (DPP-4) inhibitors

A

(also known as the ‘gliptins’)
Inhibit the breakdown of incretins by the DPP-4 enzyme.
= the increased circulating incretins (such as GLP-1 and gastric inhibitory polypeptide) promote glucose-dependent insulin release from the pancreas

Weight-neutral

32
Q

Posterior pituitary hormones

A

Oxytocin and ADH

33
Q

Tanner stages

A

Development before puberty scale

5 stages

34
Q

Characteristic histology finding in papillary thyroid cancer

A

Orphan Annie eyes with psammoma bodies

35
Q

What is the commonest bacterial cause of Waterhouse-Friderichsen syndrome (adrenal haemorrhage)?

A

Neisseria meningitidis

36
Q

Three unique signs of Graves disease

A

thyroid eye disease, thyroid acropachy, and pretibial myxoedema

37
Q

Test to diagnose diabetes insipidus

A

Water deprivation test

38
Q

Features of Multiple endocrine neoplasia (MEN) type IIb

A

Medullary thyroid cancer, phaeochromocytoma, marfanoid body habitus

39
Q

Magnesium levels must be checked in a hypoparathyroid biochemistry

A

Magnesium allows parathyroid hormone to exert its effects: magnesium enables secretion and function of parathyroid hormone.

40
Q

What is the first hormone to be secreted in response to hypoglycaemia?

A

Glucagon

41
Q

What antibodies are present in 90% of Hashimoto’s thyroiditis cases?

A

Anti-thyroid peroxidase (anti-TPO) antibodies

42
Q

Why does primary hyperparathyroidism cause hypophosphataemia?

A

Parathyroid hormone causes a decrease in renal phosphate reabsorption - excessive levels of PTH, as found in hyperparathyroidism, can lead to low serum phosphate levels due to reduced renal reabsorption.

43
Q

Why can risperidone cause galactorrhoea?

A

Risperidone is an atypical antipsychotic. All antipsychotics have the potential to raise prolactin. This is because they inhibit dopamine, subsequently reducing dopamine-mediated inhibition of prolactin.

44
Q

Why does treatment of DKA present with hypokalaemia?

A

Treatment = Insulin: decreases serum potassium through stimulation of the Na+/K+ ATPase pump

45
Q

What is the half life of insulin in the circulation of a normal healthy adult?

A

> 30 minutes

46
Q

Water deprivation test in primary polydipsia

A

urine osmolality after fluid deprivation: high

urine osmolality after desmopressin: high

47
Q

Which is the primary ketone body involved in diabetic ketoacidosis?

A

acetoacetate (as well as b-hydroxybutyrate)

breakdown product = acetone

48
Q

Ketone bodies

A

Produced by the liver from fatty acids.

Produced during periods of fasting/starvation, intense exercise, or in untreated type 1 diabetes mellitus.

They are picked up by the extra-hepatic tissues, and converted into acetyl-CoA which then enters the citric acid cycle and is oxidized in the mitochondria for energy.

49
Q

Why does alcohol cause a late hypoglycaemia?

A

Carbohydrates in alcoholic drinks can cause blood glucose to rise. This is then followed by the alcohol inhibiting glycogenolysis = late hypoglycaemia.

50
Q

Hypoglycaemia (plasma glucose level of less than 4.0 mmol/L) treatment

A

If the patient is conscious and able to swallow the first-line treatment is a fast-acting carbohydrate by mouth i.e.. glucose liquids, tablets or gels

If the patient is unconscious or unable to swallow, subcutaneous or intramuscular injection glucagon may be given.
Alternatively, intravenous 20% glucose solution may be given through a large vein

51
Q

How does Cushing’s affect potassium concentration?

A

Results in hypokalaemia

In high concentrations cortisol can exhibit mineralocorticoid (e.g. aldosterone) activity by binding to and activating Na+/K+ pumps. This causes the movement of potassium into the cells and can result in hypokalaemia.

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