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Pathology (Guide) > Chemical Pathology - Pituitary > Flashcards

Chemical Pathology - Pituitary Flashcards

1
Q

What hormones are produced by the hypothalamus?

A
  • GHRH
  • GnRH
  • TRH
  • Dopamine
  • CRH (corticotrophin-releasing hormone)
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2
Q

Which hormones are produced by the anterior pituitary?

A
  • GH
  • LH
  • FSH
  • TSH
  • Prolactin
  • ACTH (adreno-corticotrophic hormone)
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3
Q

Which hormones produced by the hypothalamus have effects on which pituitary hormones, and what kind of effect?

A
  • GHRH > Stimulates GH
  • GnRF > Stimulates LH + FSH
  • TRH > Stimulates TSH + Prolactin
  • Dopamine > Inhibits Prolactin
  • CRH > Stimulates ACTH
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4
Q

What hormone inhibits GH and where is it produced?

A

Somatostatin (Pancreas)

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5
Q

Where does GH act and what does it produce?

A

Liver
- IGF-1
- IGF-2

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6
Q

Where does TSH act and what does it produce?

A

Thyroid
- T3
- T4

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7
Q

Where does prolactin act and what does it produce?

A

Breast
- Milk

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8
Q

Where does ACTH act and what does it produce?

A

Kidneys
- Cortisol

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9
Q

What is Sheehan’s Syndrome?

A

Pituitary apoplexy (ischaemia of pituitary gland) secondary to PPH

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10
Q

What is the MoA of an antipsychotic?

A
  • Dopamine antagonists
  • Act on D2-receptors
  • Increase prolactin production
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11
Q

What are some contraindications to a combined pituitary test?

A
  • Ischaemic heart disease
  • Epilepsy
  • Untreated hypothyroidism (impairs GH + cortisol response)
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12
Q

What are some side effects to the combined pituitary test?

A
  • Sweating
  • Palpitations
  • LOC
  • Convulsions with hypoglycaemia (rarely)

TRH Injection:
- Metallic taste in mouth
- Flushing
- Nausea

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13
Q

What is the process of the combined pituitary function test?

A
  • Administer LHRH (GnRH), TSH + Insulin
  • Measure pituitary hormone levels at 0, 30, 60, 90 + 120 minutes + glucose
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14
Q

Why is insulin given in the combined pituitary function test?

A

To induce stress to cause a hypoglycaemic state, thus triggering GH + ACTH

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15
Q

What is the procedure for the combined pituitary function test?

A
  1. Fast pt overnight, ensure good IV access, weigh pt
  2. Mix into 5ml syringe (insulin - 0.15IU/kg, 200ug TRH + 100ug LHRH), give IV
  3. Chest bloods every 30 mins + up to 2 hours
  4. Replacement: urgent hydrocortisone, T4, oestrogen + GH
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16
Q

Which hormone levels are measured for up to one hour only and which are measured for up to 2 hours in the combined pituitary function test?

A
  • Glucose, cortisol, GH for 2 hours
  • Thyroxine plus glucose, FHS, TSH, prolactin for 1 hour
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17
Q

What is the outcome of insulin tolerance test?

A
  • Adequate cortisol response (increase >170nmol/L)
  • Adequate GH response (increase >6ug/L)
18
Q

What is the outcome of the thyrotrophin releasing hormone test?

A
  • Normal result = TSH rise >5mU/L
  • Hyperthyroidism = TSH remains suppressed
  • Hypothyroidism = Exaggerated response
  • Not needed to diagnose hyperthyroidism anymore
19
Q

What is the outcome of the gonadotrophin releasing hormone test?

A
  • Normal: peaks at 30-60mins; LH >10U/L, FSH >2U/L
  • Inadequate response = early indication of hypopituitarism
  • Pre-pubertal children should have no response of LH/FSH to LHRH
20
Q

How is a gonadotrophin deficiency diagnosed?

A
  • Basal levels, not dynamic testing
  • Males = low testosterone in absence of raised basal gonadotrophins
  • Females = low oestradiol without elevated basal gonadotrophins + no response to clomiphene
21
Q

What is a microadneoma?

A
  • <10mm
  • Usually benign (prolactinoma)
22
Q

What is a macroadenoma?

A
  • > 10mm
  • Aggressive
  • Usually non-functioning
23
Q

What can happen as a result of a pituitary tumour?

A

Compression of the optic chiasm leading to bitemporal hemianopia

24
Q

What are some generic symptoms of a pituitary tumour?

A
  • Bitemporal hemianopia/superior quadrantanopia
  • Headache
  • Hormone-related symptoms
25
Q

What are some symptoms of acromegaly?

A
  • Soft tissue growth (hands, feet, tongue)
  • Organomegaly
  • Sx of HF, HTN, Diabetes
  • Carpal tunnel
26
Q

How does a non-functioning adenoma lead to increased prolactin levels?

A
  • It can crush the stalk, increasing levels but lowering dopamine inhibition as there’s reduced blood flow
  • Increased prolactin will be relatively small
27
Q

What are the 3 types of prolactinaemia, their classification + causes?

A

Mild elevation (<1000 miu/L)
- Stress
- Recent breast examination
- Vaginal examination
- Hypothyroidism
- PCOS

Moderate elevation (>1000 miu/L, <5000 miu/L)
- Hypothalamic tumour
- Non-functioning pituitary tumour compressing hypothalamus
- Microprolactinoma
- PCOS
- Drugs (e.g. phenothiazides, domperidone)

Extreme elevation (>5000 miu/L)
- Macroprolactinoma

28
Q

What’s the most common pituitary tumour, its symptoms and investigation findings?

A

Prolactinoma

Sx:
- Amenorrhoea
- Galactorrhoea Sx (gynaecomastia, loss of libido, impotence)

Ix:
- Increased prolactin (>6000)
- No increase in GH + cortisol

29
Q

What is the management for a prolactinoma?

A
  1. Replacements (hydrocortisone, T4, oestrogen, GH) + D2 agonists (cabergoline, bromocriptine)
  2. Transphenoidal excision (if visual/pressure sx not responding to medical Tx)
30
Q

What is the second most common pituitary tumour, its investigation findings and management?

A

Non-functioning pituitary adenoma

Ix:
- Increased prolactin (1000-5000)

Mx:
- D2 agonists (cabergoline/bromocriptine)
- Watch + wait if asymptomatic

31
Q

What is the gold standard investigation for acromegaly + its management?

A

Ix:
- OGTT: Increased GH (even before baseline), Increased prolactin, no increase in cortisol

MX:
1. Transphenoidal surgery
2. Pituitary radiotherapy
3. Cabergoline
4. Octreotide (somatostatin analogue) -> can’t be stopped once started
5. GH antagonist (pegvisomant)

32
Q

What is the follow-up for a patient with Acromegaly?

A

Yearly:
- GH, IGF-1 +/- OGTT
- Visual fields
- Vascular assessment
- BMI
- Photos

33
Q

What are some clinical signs of a patient with acromegaly?

A
  • High glucose
  • High calcium
  • High phosphate
34
Q

What hormones are produced in the posterior pituitary, where do they act and what is the result?

A

ADH (vasopressin)
- Blood vessels (vasoconstriction = V1)
- Kidneys (water resorption = V2)

Oxytocin
- Breast (lactation)
- Uterus (childbirth)

35
Q

What can cause an excess in ADH?

A

Lung
- Lung paraneoplasias (small cell lung cancer, pneumonia)

Brain
- TBI
- Meningitis
- Primary/secondary tumours

Iatrogenic
- SSRIs
- Amitrptylline
- Carbamazepine
- PPIs

Effect
- SIADH (euvolaemic hyponatraemia)

36
Q

What can cause ADH failure and how?

A
  • Diabetes insipidus: increased diuresis due to failure of production or insensitivity to ADH, leads to decreased urine osmolality + increased serum osmolality
37
Q

What are the different types of diabetes insipidus and their causes?

A

Neurogenic (failure of production)
- 50% = idiopathic

Nephrogenic
- Iatrogenic
- Lithium
- Hypercalcaemic
- Renal failure

Dipsogenic (failure/damage to hypothalamus + thist drive, hypernatraemia without increased thirst response)

38
Q

What are some symptoms of hypopituitarism?

A
  • Lethargy
  • Weight gain
  • Hypotension
  • Hair loss
  • Myalgia
  • Hormone-specific sx
39
Q

What is the management of hypopituitarism?

A

Hormone-replacement (start with hydrocortisone)

40
Q

What are some causes of hypopituitarism?

A
  • Infection = meningitis (TB)
  • Inflammation = sarcoidosis
  • Malignancy = pituitary adenomas (functioning + non-functioning)
  • Vascular = Sheehan’s syndrome, pituitary apoplexy
  • Iatrogenic = surgery + radiation
  • Tertiary = Kallman’s syndrome

Pathology (Guide) (84 decks)

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