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Year 2 Clinical > Pituitary Gland: Non-Functioning Tumours, Prolactinoma, Acromegaly > Flashcards

Pituitary Gland: Non-Functioning Tumours, Prolactinoma, Acromegaly Flashcards

1
Q

Hormones released by the anterior pituitary?

A

ACTH (stimulates adrenal glands)

TSH (stimulates thyroid glands)

FSH and LH (stimulate reproductive glands)

PRL (stimulates mammary glands)

STH (stimulates body parts)

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2
Q

Hormones released by the posterior pituitary?

A

ADH (stimulates urine collection channels in the kidney)

Oxytocin (stimulates mammary glands and smooth muscles above the uterus)

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3
Q

Method of hormone release from the anterior pituitary?

A
  1. Stimulatory and inhibitory hormones are released from the body of the nerve cells in the hypothalamus
  2. Secretions are 1st absorbed by capillaries in the hypothalamus base and are then transported by blood vessels to the 2nd capillary network in the anterior pituitary
  3. Stimulatory/inhibitory hormones leave the capillaries and affected the pituitary gland in secretion of hormones
  4. Hormones leave the pituitary gland through small vessels connected to the general bloodstream
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4
Q

Method of hormone release from the posterior pituitary?

A
  1. ADH and oxytocin are synthesised in the body of the nerve cells within the hypothalamus
  2. Neuron that secretes ADH and oxytocin moves downwards from the axon and gathers at the axon tip
  3. Hormones, transported with axons to the posterior lobe of the pituitary gland, enter the bloodstream from here
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5
Q

Describe the thyroid axis

A

Cold exposure stimulates temperature receptor in the hypothalamus, resulting in production of:
• Thyrotrophin-releasing hormone

This stimulates the anterior pituitary to release:
• Thyrotrophin

This stimulates the thyroid gland, resulting in production of thyroxine; this can -vely feedback to switch off thyrotrophin production

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6
Q

Describe the hypothalamo-pituitary testicular axis

A

Hypothalamus releases GnRH, which stimulates LH and FSH release

These stimulate testosterone release

-ve feedback occurs to switch off LH and FSH production

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7
Q

Describe the steroid hormone axis

A

Hypothalamus release CRH (corticotrophin-releasing hormone), which stimulates the pituitary gland to release ACTH

This stimulates the adrenal glands to produce cortisol which:
• Regulates BG levels
• Increases fat in the body
• Help in defence against infection
• Helps response to stress

Cortisol can -vely feedback to switch off production of both ACTH and CRH

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8
Q

Which hormones are controlled in a stimulatory fashion?

A

CRH (produced by the hypothalamus) stimulates ACTH release from the pituitary, which, in turn, causes release of cortisol

TRH (hypothalamus) stimulates TSH release from the pituitary, which, in turn, causes thyroxine release

GnRH (hypothalamus) stimulates LF/FSH release from the pituitary, which, in turn, causes E2 (oestradiol) release

GHRH (hypothalamus) stimulates GH release from the pituitary

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9
Q

Which hormones are controlled in an inhibitory fashion?

A

Dopamine INHIBITS prolactin production (this is the control on the hormone)

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10
Q

Which hormones are stored before exerting an effect?

A

Vasopressin and oxytocin are stored in the posterior pituitary and then exert their effects directly

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11
Q

3 principle problems in endocrinology?

A
  1. Too much hormone
  2. Too little hormone
  3. Gland is larger than usual

The pituitary gland be doing all 3 simultaneously

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12
Q

Paired hormones (pituitary and peripheral)

A

ADD TABLE GREEN

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13
Q

Baseline tests for checking pituitary function?

A

TSH and thyroxine (fT4)

LH/FSH and E2

GH and IGF-1

PRL

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14
Q

Local compression that may occur with a pituitary tumour?

A

If the tumour grows upwards (most common), can compress the optic chiasma

If the tumour grows to the right and left, can compression the cavernous sinus

A tumour can wrap around the internal carotid artery (high risk surgery, e.g: stroke)

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15
Q

Basic principles of dynamic testing in the endocrinology scenarios of:

  1. Too much hormone
  2. Too little hormone

?

A
  1. If there is too much hormone, do a test that attempts to SUPPRESS THE HORMONE
  2. If there is too little hormones, do a test that attempts to STIMULATE THE HORMONE
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16
Q

Examples of dynamic pituitary function tests that are stimulatory?

A

Synacthen (synthetic ACTH) - attempts to stimulate cortisol

Insulin stress test (GOLD STANDARD) OR prolonged glucagon test - attempts to stimulate cortisol and GH

Water deprivation test - attempts to stimulate ADH

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17
Q

Describe the synacthen test

A

Uses synthetic ACTH to stimulate cortisol, which is checked every 30 minutes

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18
Q

Describe the insulin stress test

A

Hypoglycaemia is purposefully induced (<2.2 mmol/L to stimulate the pituitary gland)

Cortisol and GH response is monitored every 30 minutes for 2-3 hours:
• Normally, cortisol should rise >500
• Normally, GH should rise >7 ug/L

19
Q

Describe the water deprivation test

A

Person is deprived of water for 8 hours; their serum and urine osmolarites are checked

Normally the urine conc. should increase and the serum conc. should remain normal

Urine : serum osmolarity ratio >2 is normal; if this is not the case, they have diabetes insipidus

20
Q

Classifications of pituitary tumours with relation to size?

A

Microadenoma is ≤ 1cm

Macroadenoma is > 1cm

21
Q

Majority of pituitary adenomas are?

A

Benign; carcinomas are rare, as are metastases from another primary tumour

22
Q

Consequences of non-functioning pituitary adenoma?

A
  • Compression on the optic chiasma
  • Compression on other structures, e.g: cranial nerve 3, 4, 6
  • Hypoadrenalism
  • Hypothyroidism
  • Hypogonadism
  • Diabetes insipidus
  • GH deficiency
23
Q

Eye symptoms with a pituitary gland tumour?

A

Bitemporal hemianopia due to compression of the posterior aspect of the optic chiasm

Temporal sides of vision is lost with this but nasal sides remain intact

24
Q

Physiological causes of raised prolactin?

A

Breast feeding

Pregnancy

Stress

Sleep

25
Q

Drug causes of raised prolactin?

A

Dopamine antagonists, e.g: metoclopramide

Anti-psychotics, e.g: phenothiazines

To a lesser extent:
• Anti-depressants, e.g: TCA and SSRIs
• Oestrogens and cocaine

26
Q

Pathological causes of raised prolactin?

A

Hypothyrodism

Stalk lesions (can be iatrogenic or due to a road-traffic accident)

Prolactinoma

27
Q

Clinical symptoms and signs of raised prolactin in females?

A 
EARLY presentation with:
• Ammenorrhoea
• Galactorrhoea (milk production from the breasts)
• Menstrual irregularity
• Infertility
28
Q

Clinical symptoms and signs of raised prolactin in males?

A 
LATE presentation with:
• Impotence (raised prolactin decreases testosterone)
• Visual field abnormalities
• Headache 
• Anterior pituitary malfunction
29
Q

Ix for prolactinoma?

A

Prolactin conc.

MRI of the pituitary

Visual field testing (for BILATERAL HEMIANOPIA)

Pituitary function tests, e.g: other hormone affected

30
Q

Features to search for on an MRI of the pituitary?

A
  • Microprolactinoma (<1 cm)
  • Macroprolactinoma (>1 cm)
  • Pituitary stalk
  • Optic chiasma
31
Q

Treatment of a prolactinoma?

A

Cebergoline (Dostinex) is given orally 2X per week; it is a DOPAMINE AGONIST

It has few side effects and reduces prolactin and tumour size

32
Q

What is acromegaly?

A

There is GH excess

In childhood, it is called gigantism

33
Q

Signs and symptoms of acromegaly?

A

Giant (before epiphyseal fusion)

Thickened soft tissues:
• Skin, large jaw, sweaty, large hands

Hypertension and cardiac failure (increased cardiac muscle)

Headaches (hyperdynamic blood supply through the brain, NOT due to compression effects of tumour)

Snoring/sleep apnoea

Diabetes mellitus

Local pituitary effects:
• Visual fields, hypopituitarism

Early CV death

Colonic polyps and colon cancer

34
Q

Ix for acromegaly?

A

IGF-1 (should correspond to the age and sex)

Glucose Tolerance Test (a type of suppression test)

Can also do:
• Visual field testing
• CT/MRI pituitary scan
• Pituitary function tests for other hormones

35
Q

Describe the GTT

A

75g of oral glucose is given

GH is checked at every 30 mins until 120 is reached

Normally, glucose should suppress GH to <0.4 ug/L

In acromegaly, GH is either:
• Unchanged
• Paradoxical rise
• Remain >1 ug/L after glucose

36
Q

Other tests for acromegaly?

A

Visual field

37
Q

Treatment of acromegaly?

A

Pituitary surgery (MAJORITY)

External radiotherapy to the pituitary fossa

38
Q

Post-operate checks in acromegaly?

A

A GH <0.4 ug/L is satiffactory

If GH >1 ug/L, they require drug therapy with:
• Dopamine agonist, e.g: Cabergoline
• Somatostatin analogues, e.g: Octreotide
• GH antagonists, e.g: Pegvisomant

39
Q

Effects of somatostatin analogues in acromegaly?

A

Reduces GH in most patients

Tumour shrinkage over 6-12 months; re-expansion occurs 6 weeks after stopping though

Relieves headache in 1 hour

40
Q

Side effects of somatostatin analogues?

A

Local stinging

Short-term:
• Flatulence, diarrhoea and abdominal pains

Long-term:
• Gastritis and gallstones

41
Q

Somatostatin analogues used in acromegaly?

A

Octreotide (subcutaneous 3X/day)

Sandostatin LAR (IM once/28 days)

Lanreotide autogel (IM once/28 days)

42
Q

Dopamine agonists used in acromegaly?

A

Cabergoline up to (3g weekly)

This works better if there is co-secretion of prolactin

43
Q

Use of pegvisomant?

A

Binds to GH receptor and blocks activity; tumour size does not decrease, in fact, sometimes, there is an increase

IGF-1 decreases but serum GH conc. may increase

Given as a last-line therapy (subcutaneous injection, 10-30 mg per day)

44
Q

Acromegaly follow-up?

A

Achieve clinically safe GH levels:
• GH <0.4 ug/L (post-GTT) and <2 ug/L (random)
• IGF-1

Check other pituitary hormones, esp. thyroid

Cancer surveillance, e.g: colon and tubulovillous adenoma

CV risk factors

Sleep apnoea

Year 2 Clinical (119 decks)

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