Investigating the endocrine system Flashcards
1
Q
Endocrine systems
A
Thyroid, Gonads, Adrenal, Leptin from adipose tissue, Ghrelin from GI to regulate hunger
2
Q
Types of hormones
A
- Peptide hormones from pituitary gland - ACTH, TSH
- Steroid hormones - testosterone, cortisol
- Tyrosine based hormones - T4 thyroxine, T3
3
Q
Fundamental pathway for all endocrine systems
A
- hypothalamus produces hormone that acts on anterior pituitary to produce second hormone which acts on endocrine organ
- hormone ALWAYS inhibit the pathway, inhibits at pituitary and hypothalamus.
4
Q
TSH low, ft4 low
A
Pituitary failure = secondary hypothyroidism
5
Q
TSH high, fT4 low
A
- Unresponsive thyroid, no response to TSH = primary hyperthyroidism
6
Q
TSH low, fT4 high
A
- Thyroid gland overproduction = primary hyperthyroidism
7
Q
Both TSH + fT4 high
A
- Pituitary overproduction = secondary hyperthyroidism
8
Q
Benefits of TSH frontline test
A
- Cheap
- Accounts for most diseases
- If TSH elevated measure fT4 to pick up hypothyroid patients
9
Q
Negatives of TSH testing
A
- If low measure T3 and T4 to pick up hyperthyroid patients
- sometimes normal TSH patients are not followed up, they can have secondary hypothyroidism as they have low fT4 – 80% hypothyroid patients would be missed
10
Q
Sick euthyroid syndrome
A
- show abnormality in thyroid function test but they are euthyroid (normal thyroid)
- Illness can supress TSH and also reduce the levels of TBG or modify its capacity to bind T3 and T4, hence increasing free thyroid hormone levels
11
Q
Why is it futile to measure thyroid function in patients in hospital
A
- Mechanisms of acute illnesses influence the hypothalamic-pituitary-thyroid axis, producing thyroid test results - discordant, do not fit recognizable patterns, difficult to interpret
12
Q
Frequency of tests during treatment
A
- Healthy = repeat 3 years
- Hyperthyroid = repeat 1-2 months after treatment
- Hypothyroid - Do not measure less than 2 months
- Thyroidectomy - serum TSH 6-8 weeks post op
13
Q
Phaeochromocytoma
A
- tumour of neuroendocrine chromaffin cells – the majority in the adrenal medulla, tumour in adrenal medulla that produces catecholamine.
14
Q
Phaeochromocytoma presentation
A
- Hypertension, sweating, pallor, panic attacks, headaches, abdominal pain or nothing as 50% found post-mortem
15
Q
Phaeochromocytoma investigations
A
- Plasmametanephrines – metabolite of catecholamines; elevated more consistently across the day
- 24h urine fractionated metanephrines - no hypertensives 24h before
