Assessing Endo Disorders?

Question 1

How is the endocrine system split?

Answer 1

Primary – End organ
Secondary – Pituitary
Tertiary – Hypothalamus

Question 2

Role of hypothalamus?

Answer 2

integration of signals + conversion of them to

a chemical messenger so that chemical messenger can go through our body

Question 3

How does pituitary gland amplify the signal?

Answer 3

contain a large amount of hormone, enough to be diluted + travel around body

Question 4

Role of end organs?

Answer 4

switch off production of central hormones, which is principle of negative feedback

Question 5

Significance of cavernous sinus?

Answer 5

various cranial nerves supplying extra-ocular muscles

Question 6

What causes double vision?

Answer 6

squashing of cranial nerves

Question 7

What causes loss of sight?

Answer 7

compressing optic chiasm

Question 8

Features of peptide hormones?

Answer 8

charged, (on average negatively due to their side
chains) act at surface receptors
->  that will act on
surface receptors
->

Question 9

Features of steroid hormones?

Answer 9

aliphatic (fat soluble) + act on nuclear receptors

Question 10

What acts on surface receptors?

Answer 10

anything that comes from brain, pituitary, gut is a peptide

Question 11

What acts on nuclear receptors?

Answer 11

anything that comes from gonads, adrenals are steroids and are fat soluble

Question 12

Principle of a dynamic test?

Answer 12

although we can’t tell what the one-off blood test means, we can tell what the extremes of physiology are. eg:

• If looking for deficiency, can see when it should be highest
• If looking for excess can see when it should be lowest

Question 13

Nomenclature of pituitary + hypothalamic hormones?

Answer 13

• LH FSH - Gonadotrophin = gonadotrophin releasing hormone
• GH - Somatotrophin = GH releasing hormone
• TSH - Thyrotrophin = thyrotrophin releasing hormone
• ACTH - Corticotrophin = corticotrophin releasing hormone
• increased Prolactin - Lactotrophin

Question 14

What happens if you take away these hormones?

Answer 14

target organ will shrink as hromones cause secretion + growth of target organ

Question 15

What’s principle of endocrine testing based on?

Answer 15

law of mass action
before used radioactive tracers, but now coloured dyes :
radioactive immunoassay (RIA)

Question 16

Describe endocrine testing

Answer 16

• have a binding site - an antibody + hormone.
• in a test-tube it forms an equilibrium
• have some bound hormone to antibody
• some free hormone + antibody
• radioactive tracer/colour marker bound to hormone
• binding site full of marker to measure
• 1st stage of measurement is constructing a curve, you put known amounts of un-labelled hormone in, which will displace some of labeled hormone so drop in radioactivity
• using a centrifuge to assess radioactivity
• bound stuff falls to the bottom
• measure amount of radioactivity in bound stuff
• put in unknown samples + measure radioactivity
• read across to see how much hormone there is

Question 17

Types of assays used for thyroid hormone testing?

Answer 17

total hormone assay

free hormone assay

Question 18

Features of total hormone assays?

Answer 18

• cheap + easy
• not reflective of free hormone levels because in plasma most hormone is bound to a binding protein, either specific or albumin to protect hormone from being broken down by enzymes before it reaches its target site
• all hormone bound to protein isn’t biologically active, it’s being stored

Question 19

Features of free hormone assays?

Answer 19

-complex + expensive
-biologically active + activates receptors on cells
-representative of active hormone fraction, not binding protein dependent
-need to get rid of all binding protein + hormone bound
to it (difficult)
-could knock off some of hormone of binding protein by accident (or get some stuck on)

Question 20

Role of thyrotrophin releasing hormone?

Answer 20

causes release of TSH

Question 21

Role of TSH?

Answer 21

acts on thyroid gland to release triiodothyronine + thyroxine (tetraiiodothyronine).

Question 22

Role of deiodinases?

Answer 22

T3 more active, so active T4 by converting it to T3

Question 23

Role of T4?

Answer 23

provides the negative feedback because T4 is an intravascular store of thyroid hormone

Question 24

Investigation of hyperthyroidism?

Answer 24

• Thyroid function test
• Autoantibodies -as most hyperthyroidism is caused by autoimmune reaction
• Technesium scanning -tells us the type

Question 25

Investigation of hypothyroidism?

Answer 25

- Thyroid function | - Autoantibodies

Question 26

Investigation of thyroiditis (irritation of thyroid gland)?

Answer 26

- Thyroid function - ESR (erythrocyte sedimentation rate) - Technesium scanning

Question 27

Role of technesium scan?

Answer 27

because technesium taken up into thyroid gland like iodine so can see where/if thyroid gland taking up iodine - tells us if cells are over-active or not Note in a condition that has proper thyrotoxicosis the gland is biologically overactive, but in thyroiditis we have a destructive process, something destroying the gland making it leaky. So it leaks its stores into the circulation, but biologically the thyroid is functioning fine. Here a technesium scan would be negative, it will not be taking up technesium because it is stunned/being destroyed.