Pituitary, Thyroid, Adrenals Flashcards
Hypothalamic Hormone - GHRH has action on which pituitary hormone(s)?
Stimulates GH
Hypothalamic Hormone GnRH has action on which hormone?
LH/FSH
Hypothalamic Hormone - TRH has action on which pituitary hormone(s)?
Stimulates TSH, Prolactin
Hypothalamic Hormone - Dopamine has action on which pituitary hormone(s)?
Inhibits Prolactin
Hypothalamic Hormone - CRH has action on which pituitary hormone(s)?
Stimulates ACTH
Combined Pituitary Function Test (CPFT) - Indications
Assessment of all components of anterior pituitary function used particularly in pituitary tumours or following tumour treatment
Combined Pituitary Function Test (CPFT) - Contraindications
Ischaemic heart disease Epilepsy Untreated hypothyroidism (impairs the GH and cortisol response)
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
Combined Pituitary Function Test (CPFT) - Interpretation
Involves interpreting three aspects 1) Insulin tolerance test 2) Thyrotrophin Releasing Hormone Test 3) Gonadotrophin Releasing Hormone Test
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
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
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
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
Posterior pituitary hormones
ADH
Oxytocin
causes of Excess ADH
Lungs - Lung paraneoplasias - SCC and Small Cell pneumonia
Brain - Traumatic Brain injury, meningitis
Iatrogenic - SSRIs, Amitryptiline
Effect - Euvolaemic Hyponatraemia
Neurogenic/ Cranial ADH failure
Failure of ADH production - 50% idiopathic
Nephrogenic ADH failure - causes
Commonly iatrogenic - Lithium, also hypercalcaemia, renal failure
Dipsogenic ADH failure
failure/ damage to hypothalamus and thirst drive, hypernatraemia without increased thirst response
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
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
Thyroid Function Tests -High TSH and Low T4
Hypothyroidism
Thyroid Function Tests -High TSH normal T4
Treated hypothyroidism or subclinical hypothyroidism (look for associated hypercholesterolaemia)
Thyroid Function Tests -High TSH and High T4
TSH secreting tumour or thyroid hormone resistance
Thyroid Function Tests -Low TSH and High T4/T3
Hyperthyroidism
Thyroid Function Tests -Low TSH and normal T4/T3
Subclinical Hyperthyroidism
Thyroid Function Tests -Low TSH and Low T4
Central hypothyroidism (hypothalamic/pituitary disorder
Thyroid Function Tests - High (later Low) TSH and Low T4/T3
Sick euthyroidism (with any severe illness)
Thyroid Function Tests -Normal TSH, abnormal T4
? Assay interference, changes in TBG, amiodarone
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
Causes of Low Uptake Hyperthyroidism
- Subacute DeQuervains Thyroiditis - self limiting post viral painful goitre
- Postpartum thyroiditis
Causes of Autoimmune Hypothyroidism
- Primary atrophic hypothyroidism - diffuse lymphocytic infiltration and atrophy. No goitre
- Hashimotos thyroiditis - Plasma cell infiltration and goitre. Elderly females. May be initial Hashitoxicosis. ++ autoantibody titres
Other causes of Hypothyroidism
- Iodine deficiency (common worldwide)
- Post thyroidectomy/radioiodine
- Drug induced - antithyroid drugs, lithium, amiodarone
Hyperthyroid - treatment
Depends on aetiology
- Low uptake - symptomatic - beta blockers, NSAIDs for dequervains
- High uptake - BB and antithroid therapy - carbimazole/propylthiouracil (prop is rarely used now due to risks of aplastic anaemia)
Can be used to block and replace or titrate TSH. Can also use radio iodine or surgery
Hypothyroid - treatment
Thyroid replacement therapy
Thyroid Neoplasia - Papillary -frequency, average age of onset, treatment
>60% of cases 30-40y surgery +/- radioiodine, Thyroxine to lower TSH
Thyroid Neoplasia - Follicular -frequency, average age of onset, appearance, treatment
25% Middle age Well differentiated but spreads early Surgery + RI + Thyroxine
Thyroid Neoplasia - Lymphoma -Risk factor
5% MALT origin (mucosa-associated lymphoid tissue) Risk factor - Chronic Hashimotos, good prognosis
Thyroid Neoplasia - Anaplastic –frequency, average age of onset, treatment
Rare Elderly Poor response to any treatment
Cushing’s syndrome -cause
Pituitary Tumour - “Cushing’s Disease” (85%)
Adrenal Tumour (10%)
Ectopic ACTH producing tumour (5%)
Iatrogenic - steroid use
Cushing’s Disease -Symptoms & Signs
Moon face Buffalo Hump Striae Acne Hypertension Diabetes Muscle weakness proximal myopathy Hirsuitism
Cushing’s Disease -Investigations
Low dose dexamethasone (0.5mg) High dose dexamethasone (2mg)
Cushing’s Disease -Treatment
Treat underlying disease - surgical removal of lesion
Addison’s Disease -Causes
Autoimmune TB Tumour deposits Adrenal haemorrhage Amyloidosis
Addison’s Disease -Symptoms & signs
High K+, low Na+ and low glucose Postural hypotension Skin pigmentation Lethargy Depression
Addison’s Disease -Investigations
SynACTHen Test
Addison’s Disease -Treatment
Hormone repalcement - Hydrocortisone/fludrocortisone if primary adrenal lesion
Conn’s Disease -Causes
Adrenal tumour
Conn’s Disease -Symptoms & Signs
Uncontrollable Hypertension, High Na+, Low K+
Conn’s Disease -Investigations
Aldosterone:Renin Ratio
Conn’s Disease -Treatment
Aldosterone antagonists/ potassium sparing diuretics - Spironolactone, eplerenone, amiloride
Pheochromocytoma -Causes
Adrenal medulla Tumour = high Adrenaline
Pheochromocytoma -Symptoms & Signs
Episodic hypertension
Arrhythmias
Death if untreated
Pheochromocytoma -Investigations
Plasma and 24h urinary metadrenaline measurement/ catecholamines & VMA
Pheochromocytoma -Treatment
Alpha blockade, beta blockade then surgery when blood pressure well controlled
