Investigating the Endocrine System

Question 1

what is a hormone?

Answer 1

hormones are ‘messenger molecules’ secreted by endocrine glands

Question 2

what are the different types of intercellular signaling?

Answer 2

1. endocrine signaling
   - signalling cell sends signalling molecules to travel through the bloodstream before meeting target cell
2. paracrine signalling
   - signalling cell sends signalling molecules straight to target cell
3. autocrine signalling
   signalling cell is also the target cell

Question 3

how do hormones decide which cells to influence

Answer 3

they can only influence cells that have specific target receptors for that particular hormone

Question 4

what are the different types of hormones?

Answer 4

Peptide hormones
steroid hormones
tyrosine-based hormones

Question 5

give some examples of peptide hormones

Answer 5

PTH
ACTH
TSH

Question 6

Give some examples of steroid hormones

Answer 6

testosterone
oestradiol
cortisol

Question 7

give some examples of tyrosine-based hormones?

Answer 7

thyroxine t4

triiodothyronine T3

Question 8

what are the three ways a steroid hormone can interact with a cell?

Answer 8

1. classical model
2. Receptor mediated endocytosis
3. Signalling through cells-surface receptors

Question 9

what is the classical model of how a steroid hormone interacts with a cell?

Answer 9

the steroid hormone dissociates from its plasma carrier protein and diffuses across the cell membrane. after gaining entry to the cell, the free hormone binds to an intracellular receptor and alters gene transcription

Question 10

what is receptor-mediated endocytosis in relation to how a steroid hormone interacts with a cell?

Answer 10

the steroid hormone, bound to its plasma carrier protein, is bought into the cell via a cell-surface receptor. the complex is broken down inside the lysosome and free steroid hormone diffuses into the cell, where it subsequently exerts its action at the genomic level or undergoes metabolism

Question 11

what is signalling through cell surface receptors in relation to how a steroid hormone interacts with a cell?

Answer 11

the free steroid hormone alters intracellular signalling by binding to cell-surface receptors. the steroid hormone could exert these effects directly or could alter signalling by blocking the actions of peptide hormones

Question 12

what are the causes of abnormal increase in plasma TBG concentrations?

Answer 12

genetic cause
pregnancy
oestrogen (cop)

Question 13

what are the causes of an abnormal decrease in plasma TBG concentrations?

Answer 13

Genetic causes
protein-losing states
malnutrition 
malabsorption
acromegaly
cushing's disease
high dose corticosteroids
severe illness
androgens

Question 14

what does a change in the level of TBG result in

Answer 14

a change in the level of free hormones

Question 15

if Thyroxine is low and TSH is low what does this indicate?

Answer 15

pituitary failure

Question 16

if thyroxine is low but TSH is high what does this indicate?

Answer 16

unresponsive thyroid

Question 17

if Thyroxine is high but TSH is low what does this indicate?

Answer 17

thyroid gland overproduction

Question 18

if both TSH and thyroxine is high what does this indicate?

Answer 18

pituitary gland overproduction or feedback fails

Question 19

If TSH is elevated and free T4 is elevated what does this suggest?

Answer 19

suggest a TSH secreting tumor

Question 20

if TSH is elevated but the free t4 levels are normal what does this suggest as the cause

Answer 20

subclinical hypothyroidism

Question 21

if the TSH levels are elevated but the free t4 levels are low what does this suggest as the cause?

Answer 21

hypothyroidism

Question 22

if the TSH levels are decreased but the levels of free T4 are elevated what does this suggest as the cause?

Answer 22

Hyperthyroidism

Question 23

if the TSH levels are decreased but the levels of free T4 are normal what does this suggest as the cause?

Answer 23

T3 toxicosis or subclinical hyperthyroidism

Question 24

if the TSH levels are decreased and the levels of free t4 is also low, make a suggestion for the cause

Answer 24

central hypothyroidism

severe illness

Question 25

what is levels of TSH and free T4 in secondary hypothyroidism

Answer 25

Normal TSH and a low fT4

Question 26

why do some patients suffering from non-thyroidal illness show abnormalities within their thyroid function test?

Answer 26

TSH level may transiently rise into the hypothyroid range in the recovery phase following a period of illness illness can also reduce the levels of TBG or modify it capacity to bind to T3 and T4, increasing the levels of free thyroid hormone levels

Question 27

how often should we repeat TFTS in a healthy person

Answer 27

3 years

Question 28

how often should we repeat TFTs after monitor ing of treatment in GRAVES disease?

Answer 28

1-2 months after radioactive iodine and if the patient remains thyrotoxic then biochemical monitoring at 4-6 week intervals after thyroiddectomy measured 6-8 weeks post op

Question 29

what is the minimum period to achieve stable concentrations after a change of dose of thyroxine?

Answer 29

2 months

Question 30

on patients stabilised on longterm thyroxine therapy how often should they have their serum TSH checked?

Answer 30

annually

Question 31

what are the 2 types of adrenal medullary tumours?

Answer 31

Phaeochromcytoma (adults) | neuroblastoma (children)

Question 32

what is phaeochromocytoma?

Answer 32

tumour of neuroendocrine chromaffin cells - the majority in the adrenal medulla

Question 33

what can excessive and often episodic release of catecholamines result in what PAROXYSMAL features?

Answer 33

Hypertension sweating, pallor panic attacks\headaches abdominal pain

Question 34

how is phaechromocytoma diagnosed?

Answer 34

- difficult due to false negatives and false positive - plasmametanephrines unstable - collect on ice - 24 hour urine fractionated metanephrines

Question 35

how do we investigate the causes of hypoglycaemia and confirm the presence of an isulinoma?

Answer 35

Whipples triad signs and symptoms of hypoglycaemia low plasma glucose level resolution of symptoms once glucose level rises

Question 36

what are some endogenous causes that are insulin mediated of hypoglycaemia?

Answer 36

``` Insulinoma nesidoblastosis NIPHS insulin antibodies reactive alimentary hypoglycaemia reactive hypoglycaemia associated with type 2 DM Idiopathic ```

Question 37

what are some endogenous causes that are insulin Independent of hypoglycaemia?

Answer 37

``` Critical Organ failure - hepatic disease - cardiac failure - renal failure Sepsis Hormone deficiency - cortisol - groth hormone -Hypopituitariusm Insulin recepto antibodies NON-Islet cell tumour ```

Question 38

what are some exogenous causes of hypoglycaemia?

Answer 38

therapeutic drugs factitious alcohol

Question 39

what are some therapeutic drugs that can have a direct effect and cause hypoglycaemia

Answer 39

``` Insulin sulfonylureas Quinine Disopyramide B2-adrenoreceptor agonists Pentamide others ```

Question 40

what drugs interact with insulin or sulphonylureas and cause hypoglycaemia

Answer 40

Biguanides PPARy agonist B-adrenoreceptor blockers ACE inhibitors

Question 41

where does insulinoma arise from

Answer 41

arises from the islets of langerhans

Question 42

how is insulinoma diagnosed?

Answer 42

diagnosed through a simple fasting blood test, - low blood sugar - high insulin - high levels of C peptide

Question 43

what is ectopic ACTH secretion most commonly associated with

Answer 43

- benign carcinoid tumours of the lung - small cell tumours of the lung - islet cell tumours of the pancreas - medullary carcinoma of the thyroid - tumours of the thymus gland