Endocrinology

Question 1

What are the major endocrine glands of the body?

Answer 1

Thyroid, adrenal, pituitary (+ hypothalamus), calcium/ parathyroid

Question 2

What are different types of hormones?

Answer 2

Proteins and peptides, steroids, tyrosine and tryptophan derivatives

Question 3

What are different types of hormone receptors?

Answer 3

G-protein coupled receptors, receptor tyrosine kinase families, receptors associated with tyrosine kinase activity, steroid hormone receptors

Question 4

What is the structure of G-protein coupled receptors?

Answer 4

7 transmembrane domain and associated G-protein complex

Question 5

What is the function of G-protein coupled receptors?

Answer 5

Main sensors of internal environment and activation of a limited number of regulatory signalling cascades

Question 6

What are many endocrine disorders associated with?

Answer 6

Defects in G-protein coupled receptors

Question 7

What is the insulin receptor?

Answer 7

Receptor tyrosine kinase

Question 8

What receptors are linked to tyrosine kinase activity?

Answer 8

Cytokine receptors

Question 9

Where are steroid hormones typically located?

Answer 9

Intracellularly = either in cytoplasm or nucleus

Question 10

How do steroid hormone receptors act?

Answer 10

Steroid/receptor complex binds DNA response elements = results in changes in gene transcription

Question 11

What are some factors that influence the ability to accurately measure hormone levels?

Answer 11

Pattern of secretion, presence of carrier proteins, interfering agents, stability of hormone, absolute concentrations

Question 12

What is the major determinant of hormone concentration?

Answer 12

Rate of secretion = typically determined by highly refined feedback loops

Question 13

What are some commonly measured hormones?

Answer 13

Thyroid hormones, steroid hormone production, growth hormone evaluation, reproductive and sex hormones, prolactin, calcium and parathyroid hormone

Question 14

What are more specialist hormone tests?

Answer 14

Renin/aldosterone, catecholamines, gut hormones

Question 15

How is thyroid hormone measured?

Answer 15

Using highly sensitive TSH assay = relies on highly regulated feedback control

Question 16

What do variations in thyroid hormone levels mean?

Answer 16

Raised TSH = hypothyroid

Lowered TSH = hyperthyroid

Question 17

When is TSH an unreliable marker of thyroid hormone?

Answer 17

During pituitary dysfunction

Question 18

What is sick euthyroid syndrome?

Answer 18

Non-thyroidal illness = characterised by low free hormone levels and inappropriately low/normal TSH

Question 19

When is thyroid function measured in sick euthyroid syndrome?

Answer 19

When considered central to the clinical picture = of limited use in acutely unwell patient

Question 20

What does measuring 9am cortisol give an indication of?

Answer 20

HPA axis function (pituitary function)

Question 21

What are some markers used to measure pituitary function?

Answer 21

FT4, FT3, TSH, IGF1, LH, FSH, E2/testosterone, U & Es, plasma/urine osmolarity

Question 22

What are some tests that can be done to investigate pituitary function?

Answer 22

Dynamic tests = formal assessment of HPA axis

Imaging = MRI

Question 23

How is the growth hormone axis assessed?

Answer 23

Formal assessment requires dynamic assessment

IGF1 measurement may indicate GH hypertension

Question 24

What does the evaluation of female sex hormones depend on?

Answer 24

The timing in the menstrual cycle

Question 25

What secrets prolactin (PRL)?

Answer 25

Lactotroph cells of the anterior pituitary

Question 26

What controls prolactin release?

Answer 26

Under tonic inhibition by hypothalamic dopamine | Secretion regulated by a short loop negative feedback

Question 27

What mediates the effects of prolactin?

Answer 27

Prolactin receptor (PRLR)

Question 28

Why is it important to understand the principles of steroid hormone synthesis?

Answer 28

Helps to understand adrenal physiology and hormone production

Question 29

What can defects in steroid hormone synthesis cause?

Answer 29

Specific endocrine disorders

Question 30

Does biochemical testing occur before imaging is done?

Answer 30

Yes

Question 31

What is dynamic testing done for?

Answer 31

Hormone excess/deficiency = hormone excess gets suppression test, hormone deficiency gets stimulation tests

Question 32

What is imaging used for?

Answer 32

To localise or characterise disease

Question 33

When is combined imaging/biochemical testing used?

Answer 33

Adrenal vein sampling, petrosal sinus sampling

Question 34

What occurs due to cortisol deficiency?

Answer 34

Adrenal insufficiency = May be due to primary adrenal failure (eg Addison’s) or pituitary disease

Question 35

What may be a cause of cortisol excess?

Answer 35

Cushing’s syndrome

Question 36

What are some examples of dynamic tests?

Answer 36

Stimulation test = Synacthen test | Suppression test = dexamethasone suppression test

Question 37

What are some features of Cushing’s syndrome?

Answer 37

Cushingoid facies, acne, hirsutism, abdominal striae, centripedal obesity, intracapsular and supraclavicular fat pads, proximal myopathy, osteoporosis, hypertension, impaired glucose tolerance

Question 38

What are the different forms of Cushing’s syndrome?

Answer 38

Cushing’s disease, ACTH independent Cushing’s, ectopic ACTH, exogenous steroids

Question 39

What are some features of Cushing’s syndrome?

Answer 39

Pituitary origin, rumour arising from corticotroph cells of anterior pituitary, most common form, more common in females, most are microadenomas

Question 40

What occurs in ACTH independent Cushing’s?

Answer 40

Bilateral macronodular adrenal hyperplasia = causes by adrenal adenoma/carcinoma

Question 41

What is the main cause of ectopic ACTH?

Answer 41

Malignancy

Question 42

What screening tests are done for Cushing’s syndrome?

Answer 42

1mg overnight dexamethasone suppression test, 24hr urinary free cortisol, midnight cortisol

Question 43

What is the formal diagnostic test done for Cushing’s syndrome?

Answer 43

Low dose dexamethasone suppression test = lack of suppression means positive for Cushing’s

Question 44

How does measuring ACTH help diagnose Cushing’s syndrome?

Answer 44

ACTH low = adrenal origin likely | ACTH raised = need more investigations to determine between Cushing’s syndrome and ectopic ACTH

Question 45

What does a rise in cortisol and ACTH on CRH tests indicate?

Answer 45

Pituitary source of Cushing’s syndrome

Question 46

Why is an MRI of the pituitary done in suspected Cushing’s syndrome?

Answer 46

To evaluate the pituitary gland | Imaging also done for possible ectopic ACTH

Question 47

When is inferior petrosal sinus sampling done in Cushing’s syndrome?

Answer 47

Used to lateralise tumour prior to surgery