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Endocrinology 2 > Pituitary Tumours > Flashcards

Pituitary Tumours Flashcards

1
Q

What are the 5 types of functioning pituitary tumours that can occur?

A

Somatotrophs can cause acromegaly. Lactotrophs can cause prolactinomas. Thyrotrophs cause TSHoma (very rare). Gonadotrophs cause gonadotrophinoma. Corticotrophs cause Cushing’s disease/corticotroph adenoma.

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2
Q

What are the 3 ways pituitary tumours can be classified?

A

Based on radiological features, function or whether it is beningn/malignant.

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3
Q

What are radiological features of pituitary tumours?

A
  1. Size. If below 1cm - microadenoma. If above - macroadenoma.
  2. Sellar/suprasellar
  3. Compressing optic chiasm or not
  4. Invading cavernous sinus or not - if it is, may not be possible to treat patient as difficult to surgically access this area without damaging internal carotid artery/cranial nerves which run through this space.
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4
Q

What are functional features of tumours?

A
  1. Excess secretion of a specific pituitary hormone

3. If no excess secretion - known as Non-Functioning Adenoma

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5
Q

What are benign vs malignant classifications ?

A

Carcinomas only make up <0.5% of pit tumours. Ki67 index used to measure mitotic index - if this is less than 3%, is benigh.

Pituitary adenomas can have benign histology but display malignant behaviour.

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6
Q

What problems does hyperprolactinaemia cause?

A

Prolactin binds to prolactin receptors on kisspeptin neurons in hypothalamus. Inhibits kisspeptin release and therefore, GnRH not stimulted. Downstream LH/FSH/Oestrogen decreased leading to oligomenorrhoea/amenorrhoea, low libido, infertility, osteoporosis.

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7
Q

What are 4 key points about prolactinomas?

A
  1. Commonest functioning pituitary adenoma
  2. Serum prolactin >5000mU/L
  3. Serum prolatin is proportion to tumour size.
  4. Normal prolactin is around 300mU/L in men and 600mU/L in women.
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8
Q

What is the presentation of prolactinomas?

A

Menstrual disturbance, Erectile dysfunction, Reduced libido, Galactorrhoea, Subfertility.

GERMS

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9
Q

What are physiological causes of elevated prolactin?

A
  1. Pregnancy/breastfeeding
  2. Stress: Exercise, Seizures or Venepuncture
  3. Nipple/Chest Wall Stimulation
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10
Q

What are 3 pathological causes of elevated prolactin?

A

Primary hypothyroidism, Polycystic ovarian syndrome, Chronic renal failure (kidneys don’t excrete prolactin properly)

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11
Q

What are 5 iatrogenic causes of high prolactin?

A
  1. Anti-psychotics
  2. SSRIs
  3. Anti-emetics
  4. High dose of oestrogen
  5. Opiates

SAAHO

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12
Q

What 2 things could be indicated by a mild elevation of prolactin with no other clinical symptoms?

A
  1. Macroprolactin

2. Stress of venepuncture

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13
Q

What is macroprolactin?

A

Monomeric prolactin is biologically active and majority of circulating is monomeric. However, macroprolactin is a circulating form of prolactin which is polymeric and is an antigen-antibody complex of monomeric prolactin and IgG. This is usually less than 5%. Assay records this as elevated but has limited bioavailability and bioactivity. Not dangerous.

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14
Q

How can stress of venepuncture be eliminated?

A

Cannulated protein series can be done taking sequential measurements every 20 minutes with indwelling cannula.

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15
Q

How is prolactinoma treated?

A

If true pathological elevation is confirmed, pituitary MRI done. Dopamine receptor agonists used first (cabergoline/bromocriptine) which is safe in pregnancy. Aim is to normalise serum prolactin and shrink the prolactinoma. Dose determined based on whether it is a micro/macroprolactinoma.

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16
Q

How do dopamine receptor agonists work?

A

Lactotrophs have D2 receptors which dopamine binds to, inhibiting prolactin release. D2 receptor agonists are selective synthetic analogues of dopamine and bind to the same receptor, reducing prolactin output.

17
Q

What occurs if pituitary tumour secretes excess GH?

A

Gigantism occurs in children while acromegaly occurs in adults.

18
Q

How is acromegaly diagnosed?

A

Insidious onset of symptoms so mean time to diagnosis is 10 years. Sweatiness, headache, macroglossia, prominent nose, prognathism, hand and feet size increased, snoring + obstructive sleep apnoea, hypertension, impaired glucose tolerance/diabetes mellitus.

19
Q

How does growth hormone act?

A

Somatotrophin acts on body tissues and stimulates liver to produce IGF-1 and IGF-2 (Somatomedin) which have similar action. Causes growth and development.

20
Q

How is acromegaly diagnosed?

A

GH release is pulsatile so one-time direct measurement unhelpful. Look for:

  1. Elevated serum IGF-1
  2. Failed suppression of GH following oral glucose load - should decrease GH in normal individual but leads to a paradoxical rise in acromegalic individual. Prolactin can be raised also and pituitary MRI needed.
21
Q

How is acromegaly treated?

A

First surgical: trans-sphenoidal pituitary surgery. Aim is to normalise serum GH and IGF-1. Prior to surgery, medical treatment used to shrink tumour or if surgical resection incomplete:
1. Somatostatin analogues e.g. octreotide
2. Dopamine receptor agonists e.g. cabergoline (D2 receptors expressed by GH secreting tumours)
Radiotherapy can also be used.

If untreated, increased cardiovascular risk.

22
Q

What are the symptoms of Cushing’s?

A 
Thin skin
Proximal myopathy
Centripetal obesity (lemon on sticks)
Diabetes, hypertension and osteoporosis
Immunosuppression (reactivation of TB)
Moon face
Striae
Mental changes (depression)
Red cheeks

MIRTS DCP

23
Q

What are the causes of Cushing’s DISEASE?

A

Taking steroids by mouth (common)
Pituitary dependent Cushing’s disease (pituitary adenoma)
Ectopic ACTH (lung cancer)
adrenal adenoma or carcinoma

Occurs due to excess cortisol/glucocorticoid

24
Q

How can the causes of Cushing’s SYNDROME be classified?

A

ACTH dependent:

  1. Corticotroph adenoma
  2. Ectopic ACTH in lungs

ACTH independent:

  1. Taking steroids by mouth
  2. Adrenal adenoma/carcinoma
25
Q

Contrast Cushing’s syndrome with Cushing’s disease

A

Cushing’s syndrome refers to excess cortisol while Cushing’s disease refers to a corticotroph adenoma secreting ACTH

26
Q

How is Cushing’s disease investigated?

A

Cortisol secretion is diurnal.

  1. 24h urine free cortisol measured - High cort secretion
  2. Elevation of late night cortisol (saliva/blood) indicating loss of diurnal rhythm
  3. Failure to suppress cortisol after oral dexamethasone (exogenous glucocorticoid) is also a sign of increased cort secretion
27
Q

What is an indicator of non-functioning pituitary adenoma?

A

Visual disturbance e.g. bitemporal hemianopia due to adenoma which doesn’t secrete any specific hormone

28
Q

What is indicated in hormone levels with a non-functioning pituitary adenoma?

A

Can present with hypopituitarism and serum prolactin might be raised as dopamine unable to travel down pituitary stalk from hypothalamus. Trans-sphenoidal surgery needed for larger tumours particularly if there is visual disturbance.

Endocrinology 2 (11 decks)

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