Endocrine tests and concepts

Question 1

Most common cause of hypothyroidism?

Answer 1

Hashimoto’s thyroiditis

Question 2

Other causes of hypothyroidism?

Answer 2

Subacute thyroiditis (de Quervain’s)
associated with a painful goitre and raised ESR

Riedel thyroiditis
fibrous tissue replacing the normal thyroid parenchyma
causes a painless goitre

Postpartum thyroiditis

Drugs
lithium
amiodarone

Iodine deficiency
the most common cause of hypothyroidism in the developing world

Question 3

Most common cause of thyrotoxicosis?

Answer 3

Graves disease

Question 4

Other causes of thyrotoxicosis?

Answer 4

toxic multinodular goitre
Amiodarone

Question 5

Antibodies in thyroid disease

Answer 5

Anti-thyroid peroxidase (anti-TPO) antibodies
TSH receptor antibodies
Thyroglobulin antibodies

Question 6

Most common antibody test positive in Graves disease

Answer 6

TSH receptor antibodies are present in around 90-100%

Question 7

Most common antibody test positive in Hashimoto’s thyroiditis

Answer 7

anti-TPO antibodies are seen in around 90% of patients

Question 8

What is the TSH / T3/T4 in HYPOthyroidism?

Answer 8

T3/T4 Low
TSH HIgh

Question 9

What is the TSH / T3/T4 in HYPERthyroidism?

Answer 9

TSH low
T3/T4 HIGH

Question 10

What is the TSH / T3/T4 in subclinical hypeothyroidism?

Answer 10

TSH raised but T3, T4 normal

Question 11

What is the TSH/T3/T4 in Secondary hypothyroidism

Answer 11

Both LOW

Question 12

What is the TSH/T3/T4 in Sick euthyroid syndrome

Answer 12

Both LOW

Question 13

Poor compliance with thyroxine TSH/T3/T4

Answer 13

T4 Normal but TSH HIgh

Question 14

Treatment of hypothyroidism?

Answer 14

Thyroxine

Question 15

Initial treatment of hyperthyroidism (Graves)

Answer 15

propanolol

Question 16

Tx of Graves disease

Answer 16

carbimazole
Radioiodine treatment

Question 17

CI of radioiodine tx

Answer 17

pregnancy
age <16
thyroid eye disease

Question 18

How does carbimazole work?

Answer 18

blocks thyroid peroxidase from coupling and iodinating the tyrosine residues on thyroglobulin → reducing thyroid hormone production

Question 19

Side effects of carbimazole?

Answer 19

agranulocytosis

Question 20

Treatment of thyroid storm?

Answer 20

symptomatic treatment e.g. paracetamol
treatment of underlying precipitating event
beta-blockers: typically IV propranolol
anti-thyroid drugs: e.g. methimazole or propylthiouracil
Lugol’s iodine
dexamethasone - e.g. 4mg IV qds - blocks the conversion of T4 to T3

Question 21

Causes of Cushings syndrome?

Answer 21

ACTH dependent causes
Cushing’s disease (80%): pituitary tumour secreting ACTH producing adrenal hyperplasia
ectopic ACTH production (5-10%): e.g. small cell lung cancer is the most common causes

ACTH independent causes
iatrogenic: steroids
adrenal adenoma (5-10%)
adrenal carcinoma (rare)
Carney complex: syndrome including cardiac myxoma
micronodular adrenal dysplasia (very rare)

Question 22

2 most commonly used tests in Cushing’s syndrome?

Answer 22

Overnight dexamethasone suppression test
24 hour urinary free cortisol

Question 23

Test result if neither ACTH / cortisol suppressed

Answer 23

Ectopic ACTH syndrome

Question 24

Test result if cushing’s disease (i.e. pituitary adenoma → ACTH secretion)

Answer 24

Both suppressed

Question 25

Adrenal adenoma acth/cortisol tests

Answer 25

cortisol not suppressed, acth suppressed

Question 26

Acromegaly cause

Answer 26

In acromegaly there is excess growth hormone secondary to a pituitary adenoma in over 95% of cases. A minority of cases are caused by ectopic GHRH or GH production by tumours e.g. pancreatic.

Question 27

Features of acromegaly

Answer 27

coarse facial appearance, spade-like hands, increase in shoe size large tongue, prognathism, interdental spaces excessive sweating and oily skin: caused by sweat gland hypertrophy features of pituitary tumour: hypopituitarism, headaches, bitemporal hemianopia raised prolactin in 1/3 of cases → galactorrhoea 6% of patients have MEN-1

Question 28

Complications of acromegaly

Answer 28

Complications hypertension diabetes (>10%) cardiomyopathy colorectal cancer

Question 29

Tests for ACROMEGALY

Answer 29

Serum IGF-1 levels have now overtaken the oral glucose tolerance test (OGTT) with serial GH measurements as the first-line test. The OGTT test is recommended to confirm the diagnosis if IGF-1 levels are raised.

Question 30

Acromegaly MX

Answer 30

Trans-sphenoidal surgery ocreotide (somatostatin analogue) pegvisomant GH receptor antagonist - prevents dimerization of the GH receptor dopamine agonists for example bromocriptine

Question 31

Normal fasting glucosse

Answer 31

Less than 6.0

Question 32

Impaired fasting glucose

Answer 32

< or = to 6.1

Question 33

Impaired glucose tolerance

Answer 33

impaired glucose tolerance (IGT) is defined as fasting plasma glucose less than 7.0 mmol/l and OGTT 2-hour value greater than or equal to 7.8 mmol/l but less than 11.1 mmol/l

Question 34

Normal glucose tolerance

Answer 34

<7.8

Question 35

Diabetes insipidus CAUSES

Answer 35

Diabetes insipidus (DI) is a condition characterised by either a decreased secretion of antidiuretic hormone (ADH) from the pituitary (cranial DI) or an insensitivity to antidiuretic hormone (nephrogenic DI).

Question 36

Causes of Cranial DI

Answer 36

idiopathic post head injury pituitary surgery craniopharyngiomas infiltrative histiocytosis X sarcoidosis DIDMOAD is the association of cranial Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy and Deafness (also known as Wolfram's syndrome) haemochromatosis

Question 37

Causes of nephrogenic DI

Answer 37

genetic: more common form affects the vasopression (ADH) receptor less common form results from a mutation in the gene that encodes the aquaporin 2 channel electrolytes hypercalcaemia hypokalaemia lithium lithium desensitizes the kidney's ability to respond to ADH in the collecting ducts demeclocycline tubulo-interstitial disease: obstruction, sickle-cell, pyelonephritis

Question 38

Investigations in DI

Answer 38

high plasma osmolality, low urine osmolality a urine osmolality of >700 mOsm/kg excludes diabetes insipidus water deprivation test

Question 39

Where is ADH secreted from

Answer 39

Posterior pituitary gland

Question 40

What does ADH do?

Answer 40

It promotes water reabsorption in the collecting ducts of the kidneys by the insertion of aquaporin-2 channels.

Question 41

What would be the water deprivation test result NORMAL

Answer 41

Starting plasma osmolality: LOW Final urine osmolality: >600 Urine osm. post-DDAVP: >600

Question 42

What would be the water deprivation test result in psychogenic polydipsia

Answer 42

Starting plasma osmolality: Low final urine: > 400 Urine osm. post-DDAVP: >400

Question 43

What would be the water deprivation test result in Cranial DI

Answer 43

Starting plasma osm: HIGH final urine < 300 urine osm post ddavp: > 600 Because the issue is with the brain so without water, normalises

Question 44

What would be the water deprivation test result in Nephrogenic DI

Answer 44

Starting plasma osm: HIGH final urine < 300 Urine osm. post-DDAVP: < 300 Doesn't matter if no water becausse issue is with the kidneys