Basics

Question 1

What are the main hormone subtypes? Name 1 example of each..

Answer 1

1. amino acids (proteins/peptides) e.g. insulin GH
2. Steroids derived from cholesterol (testosterone)
3. Tyrosine and tryptophan derivatives (adrenaline)

Question 2

What are the main hormone receptor types?

Answer 2

G-protein coupled receptors
Receptor Tyrosine Kinase (RTK) Families
Receptors associated with tyrosine kinase activity
Steroid hormone receptors

Question 3

What are the key features of G protein coupled receptors?

Answer 3

1. 7 transmembrane domain
2. Activates cascade of reaction e.g. cAMP resulting in desired cellular response
3. Many Endocrine disorders associated with defects in GPCRs

Question 4

What are the features of steroid hormone receptors?

Answer 4

1. typically intracellular - either in the cytoplasm or nucleus
2. the steroid receptor complex will usually bind to the nucleus to induce changes in gene transcription

Question 5

What is the hypothalamic pituitary axis?

Answer 5

Hypothalamus secretes neurohormones to pituitary gland
Stimulates pituitary gland to release hormones that affect peripheral gland

regulated by -ve feedback loop

Question 6

What factors should you consider when measuring hormones?

Answer 6

Pattern of secretion
The presence of carrier proteins (i.e. thyroblobulin and free T3)
Interfering agents
Stability of hormone (consider ½ life)
Absolute concentrations

Question 7

When might TSH not be a reliable marker of Thyroid status ??

Answer 7

Pituitary dysfunction
(“secondary hypothyroidism” or TSHoma)

Question 8

What is sick euthyroid syndrome?

Answer 8

FREE thyroid hormones are at LOW levels.
Low/normal TSH
There is no thyroid dysfunction.
Usually seen in acutely unwell patients i.e. starvation, critical illness

Question 9

What is the significance of random cortisol measurement? Why?

Answer 9

Insignificant

Cortisol secretion oscillates over 24 hrs - this is known as circadian cortisol secretion.

Question 10

GH and gonadal hormones both have pulsatile secretion natures. This makes random measurements unreliable

Answer 10

T

Question 11

How do we assess pituitary function?

Answer 11

Free T3, Free T4, Thyroid stimulation hormone
9am cortisol
Prolactin
Luteinising hormone, free stimulating hormone, testesterone
Us&Es
IGF1

Question 12

9AM cortisol measurement may give indication of Hypothalamus/piuitary/adrenal axis

Answer 12

T

Question 13

Which measurement may indicate growth hormone hypersecretion?

Answer 13

Insulin like growth factor 1 (IGF1)

Question 14

Evaluation of female sex hormones depend on timing in menstrual cycle

Answer 14

T

Question 15

Prolactin (PRL) secreted by - cells of the - pituitary

Answer 15

lactotroph, anterior

Question 16

Prolactin is under tonic inhibition by hypothalamic -

Answer 16

dopamine

Question 17

What are the principles of pituitary testing?

Answer 17

Biochemical test before imaging
Dynamic testing to detect excess/defecit
- Hormone excess- supression test
- Hormone deficiency – stimulation test
Imaging to characterise/localise disease

Question 18

Which type of dynamic test is required for Cushing’s?

Answer 18

Hormone supression test

Cushing’s is an excess of cortisol

Question 19

What are the causes of Cushing’s?

Answer 19

(Endogenous) Pituitary: tumour arising from lactotroph cells of anterior pituitary
(Endogenous) Adrenal: ACTH independent - adrenal adenoma/carcinoma or hyperplasia
Exogenous: Steroid use

Question 20

What are the screening tests for Cushing’s syndrome?

Answer 20

Overnight Dexamethasone suppression test - dexamethasone is a corticosteroid, affects levels of cortisol through negative feedback loop.
Failure to suppress = Cushing’s

Measure of ACTH
Low ACTH adrenal origin likely

Question 21

Hypothalamus releases -
Stimulates pituitary to release -
Adrenals release cotrisol

Answer 21

Corticotrophin releasing hormone

Adrenocorticotrophic hormone

Question 22

In Cushing’s syndrome rise in cortisol & ACTH on CRH test indicates - source

Answer 22

pituitary source