Pituitary, Thyroid, Adrenals Flashcards Preview

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Flashcards in Pituitary, Thyroid, Adrenals Deck (54)
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1

Hypothalamic Hormone - GHRH has action on which pituitary hormone(s)?

Stimulates GH

2

Hypothalamic Hormone GnRH has action on which hormone?

LH/FSH

3

Hypothalamic Hormone - TRH has action on which pituitary hormone(s)?

Stimulates TSH, Prolactin

4

Hypothalamic Hormone - Dopamine has action on which pituitary hormone(s)?

Inhibits Prolactin

5

Hypothalamic Hormone - CRH has action on which pituitary hormone(s)?

Stimulates ACTH

6

Combined Pituitary Function Test (CPFT) - Indications

Assessment of all components of anterior pituitary function used particularly in pituitary tumours or following tumour treatment

7

Combined Pituitary Function Test (CPFT) - Contraindications

Ischaemic heart disease Epilepsy Untreated hypothyroidism (impairs the GH and cortisol response)

8

Combined Pituitary Function Test (CPFT) - Side Effects

-Sweating, palpitations, loss of consciousness -Rarely - convulsions with hypoglycaemia -Patients should be warned that the TRH injection they may experience transient symptoms of - metallic taste in mouth, flushing and nausea

9

Combined Pituitary Function Test (CPFT) - Interpretation

Involves interpreting three aspects 1) Insulin tolerance test 2) Thyrotrophin Releasing Hormone Test 3) Gonadotrophin Releasing Hormone Test

10

Combined Pituitary Function Test (CPFT) - Interpretation -Insulin tolerance test

-Adequate cortisol response = Increase greater than 170 nmol/l to above 500nmol/l

             > below 170 = Cushings 

-Adequate GH response = Increase greater than 6mcg/L

11

Combined Pituitary Function Test (CPFT) - Interpretation -Thyrotrophin Releasing Hormone Test

-The normal result is a TSH rise to >5mU/l (30min value >60min value -If the 60min sample > 30min value - indicated primary hypothalamic disease)

-Hyperthyroidism = TSH remains suppressed

-Hypothyroidism = exaggerated response

-With the current sensitive TSH assays basal levels are now adequate and dynamic testing is not usually needed to diagnose hyperthyroidism

12

Combined Pituitary Function Test (CPFT) - Interpretation -Gonadotrophin Releasing Hormone Test

-Normal peaks can occur at either 30 or 60 minutes

-LH should >10U/l and FSH should >2U/l

-An inadequate response = possible early indication of hypopituitarism

-Gonadotrophin deficiency is diagnosed on the basal levels rather than the dynamic response

            -Males = Low testosterone in the absence of raised basal gonadotrophins

             - Females = low oestradiol without elevated basal gonadotrophins and no response to clomiphene -Pre-pubertal children should have no response of LH or FSH to LHRH

-IF sex steroids are present (i.e. precocious puberty), the pituitary will be 'primed' and will therefore respond to LHRH. Priming with steroids MUST NOT occur before this test

13

Pituitary Tumours - size and effects

Can produce any combination of pituitary hormones

-Microadenoma less than 10mm, benign 

-Macroadenoma greater than 10mm, aggressive

Can compress optic chiasm = bitemporal hemianopia

14

Posterior pituitary hormones

ADH

Oxytocin

15

causes of Excess ADH

Lungs - Lung paraneoplasias - SCC and Small Cell pneumonia

Brain - Traumatic Brain injury, meningitis

Iatrogenic - SSRIs, Amitryptiline

 

Effect - Euvolaemic Hyponatraemia

16

Neurogenic/ Cranial ADH failure

Failure of ADH production - 50% idiopathic

17

Nephrogenic ADH failure - causes

Commonly iatrogenic - Lithium, also hypercalcaemia, renal failure

18

Dipsogenic ADH failure

failure/ damage to hypothalamus and thirst drive, hypernatraemia without increased thirst response

19

Oxytocin -effects? -if pathologically low, what can you give? -antagonist?

Acts to increase uterine contractions and expulsion of milk. Not commonly pathological- if in failure of production syntocinon can be given to help stimulate breast feeding. Oxytocin antagonist Atosiban used in tocolysis

20

Normal values of

-TSH

-Free T4

-Free T3

TSH - 0.33-4.5 mu/L

Free T4 - 10.2-22.0 pmol/L

Free T3 - 3.2-6.5 pmol/L

21

Thyroid Function Tests -High TSH and Low T4

Hypothyroidism

22

Thyroid Function Tests -High TSH normal T4

Treated hypothyroidism or subclinical hypothyroidism (look for associated hypercholesterolaemia)

23

Thyroid Function Tests -High TSH and High T4

TSH secreting tumour or thyroid hormone resistance

24

Thyroid Function Tests -Low TSH and High T4/T3

Hyperthyroidism

25

Thyroid Function Tests -Low TSH and normal T4/T3

Subclinical Hyperthyroidism

26

Thyroid Function Tests -Low TSH and Low T4

Central hypothyroidism (hypothalamic/pituitary disorder

27

Thyroid Function Tests - High (later Low) TSH and Low T4/T3

Sick euthyroidism (with any severe illness)

28

Thyroid Function Tests -Normal TSH, abnormal T4

? Assay interference, changes in TBG, amiodarone

29

Causes of High Uptake Hyperthyroidism

-Graves disease - 40-60%, F>M (9:1), autoantibodies ++, high uptake on isotope scan

-Toxic multinodular goitre- 30-50%, high uptake

-Toxic adenoma - 5%, hot nodule on isotope scan

30

Causes of Low Uptake Hyperthyroidism

-Subacute DeQuervains Thyroiditis - self limiting post viral painful goitre

-Postpartum thyroiditis