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Endocrine week 4 > Hypothalmic pituitary axis physiology > Flashcards

Hypothalmic pituitary axis physiology Flashcards

1
Q

What are the hormones secreted by the anterior pituitary gland ?

A
  • TSH, ACTH, FSH, LH
  • GH and Prolactin
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2
Q

What are the hormones secreted by the posterior pituitary gland?

A

ADH and oxytocin

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3
Q

What are some of the pathologies affecting the anterior pituitary gland ?

A

Hyperfunction:

  • Adenoma
  • Carcinoma

Hypofunction:

  • Surgery/radiation
  • Sudden Haemorrhage into gland
  • Ischaemic necrosis - Sheehan Syndrome
  • Tumours extending into sella
  • Inflammatory conditions (Sarcoidosis)
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4
Q

What are some of the pathologies affecting the posterior pituitary gland ?

A

Diabetes Insipidus:

  • Lack of ADH secretion
  • Can lead to life threatening dehydration

Syndrome of Inappropriate ADH secretion (SIADH):

  • Ectopic secretion of ADH by tumours
  • Primary disorder in the pituitary
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5
Q

What is the most common pituitary tumour ?

A

Pituitary adenomas

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6
Q

How do pituitary adenomas arise ?

A

Either sporadic or may be due to MEN1 syndrome

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7
Q

How can pituitary adenomas be classified ?

A

Size (a microadenoma is <1cm and a macroadenoma is >1cm)

Hormonal status (a functional adenoma produces and excess of a particular hormone and a non-functional adenoma does not produce a hormone to excess)

Hormones produced in excess include:

  • Prolactin (20-30%)
  • ACTH (10-15%)
  • FSH/LH (10-15%)
  • GH (5%)
  • Can produce more than one
  • hormone production may be at subclinical levels
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8
Q

What are the typical features of pituitary adenomas ?

A
  • Functional tumours - Excess of a hormone (e.g. Cushing’s disease due to excess ACTH, acromegaly due to excess GH or amenorrhea and galactorrhea due to excess prolactin)
  • Non-functioning tumours or those causing compression of normal pituitary gland - present with generalised hypopituitarism
  • Headaches
  • Compression of optic chiasm - bitemporal heminopia
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9
Q

What investigations are required for someone with a suspected pituitary adenoma ?

A
  • a pituitary blood profile (including: GH, prolactin, ACTH, FH, LSH and TFTs)
  • formal visual field testing
  • MRI brain with contrast
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10
Q

What is the principle of endocrine dynamic function tests ?

A
  • If there is too much hormone being secreted resulting in a condition - do a test to suppress the hormone
  • If there is too little hormone being secreted resulting in a condition - do a test to try and stimulate it
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11
Q

What are the different dynamic pituitary stimulation tests which can be done ?

A
  1. Synacthen (synthetic ACTH) test - stimulates cortisol
  2. Insulin stress test or prolonged glucagon test - stimulates cortisol and GH
  3. Water depravation test - stimulates ADH, check serum and urine omolarities
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12
Q

What is the water deprivation test used to diagnose ?

A

Diabetes insipidus

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13
Q

What is the synacthen test used to help diagnose ?

A

Adrenal insufficiency as measures cortisol response e.g. due to additions disease

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14
Q

What is the insulin stress test (insulin tolerance test) used to asses ?

A

Assesses GH and ACTH ==> cortisol

It is the gold standard for assessing integrity of hypothalmic-pituitary adrenal axis

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15
Q

What is the relationship between dopamine and prolcatin ?

A

Dopamine inhibits prolactine secretion

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16
Q

What are some of the non-pathological causes of raised prolcatin ?

A
  • Breast feeding
  • Pregnancy
  • Stress
  • Drugs - dopamine antagonists e.g. metoclopramide, or antipsychotics e.g. phenothiazines
17
Q

What are some of the pathological causes of raised prolactin ?

A
  • Hypothyroidism
  • Stalk lesions - e.g. due to iatrogenic, road accidents
  • Prolactinoma
18
Q

What are some of the clinical signs of raised prolcatin in females ?

A
  • Galactorrhoea - milky discharge from nipples
  • Menstrual irregularity
  • Ammenorrhoea
  • Infertility
  • Osteoporosis
19
Q

What are some of the clinical features of raised prolactin in males?

A
  • Erectile dysfunction (impotence), loss of libido, galactorrhoea
  • Decreased body and facial hair
  • Uncommonly, enlarged breasts (gynecomastia)
  • Visual field abnormal
  • Headache
20
Q

What investigations are done to diagnose a prolactinoma ?

A
  • Serum prolactin
  • Pituitary MRI
  • Check visual fields - would be a bitemporal heminopia
21
Q

What is the treatment of a prolactinoma ?

A
  • 1st line dopamine agonist - Cabergoline, bromocriptine
  • 2nd line = transphenoidal surgery
22
Q

What is acromegaly ?

A

Abnormal growth of the hands feet and face caused by overproduction of GH by the pituitary gland

23
Q

What is the cause of acromegaly usually ?

A
  • 95% of patients - secondary to a pituitary adenoma
  • A minority of cases are caused by ectopic GHRH or GH production by tumours e.g. pancreatic.
24
Q

What are the characteristic features of acromegaly ?

A
  • Gaint (tall)
  • Thickened skin
  • Large hands (spade-like) & shoe-size
  • Large tongue
  • Prognathism = protrusion of lower jaw
  • Excessive sweating & oily skin
  • Snoring/sleep aponea
  • DM
  • Features of pituitary tumour: hypopituitarism, headaches, bitemporal hemianopia
25
Q

How is acromegaly diagnosed?

A
  • 1st line = Measure serum insulin-like growth factor 1 (IGF-1) + serial serum growth hormone (GH)
  • 2nd line (done to confirm diagnosis if IGF-1 levels are raised) Oral glucose tolerance test (OGTT) - measure GH during it as when given glucose GH levels should decrease but in acromegaly they remain unchanged
26
Q

What is the treatment of acromegaly ?

A

1st line = pituitary surgery (transsphenoidal)

Then retest using OGTT

2nd line = somatostatin analogue (octreotide or lanreiotide) + dopamine agonist (carbergoline)

27
Q

What are the complications of acromegaly ?

A
  • hypertension
  • diabetes (>10%)
  • cardiomyopathy
  • colorectal cancer
28
Q

What are the common side effects of somatostatins ?

A
  • Flatulence
  • Diarrhoea
  • Abdominal pains
  • Gastritis
  • Gallstones

Endocrine week 4 (8 decks)

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