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4. Metabolism > 17. Pituitary Disorders > Flashcards

17. Pituitary Disorders Flashcards

1
Q

What is the hypothalamo-pituitary axis?

A

Communication of hypothalamus and pituitary, the link between endocrine and nervous system, endocrine response to the external environment.

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2
Q

What are the seven points in the anatomy of pituitary?

A

Pituitary gland, optic chiasm, pituitary stalk, cavernous sinus, internal carotid artery, anterior pituitary and posterior pituitary.

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3
Q

What does the posterior pituitary gland secrete?

A

ADH and oxytocin.

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4
Q

What does the anterior pituitary gland secrete?

A

Growth hormone, ACTH, LH/FSH and prolactin.

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5
Q

What is the importance of growth hormone?

A

Growth and metabolism.

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6
Q

How does growth hormone act?

A

Via IGF-1 produced by the liver.

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7
Q

How is the growth hormone axes controlled?

A

GHRH stimulates GH but somatostatin inhibits it.

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8
Q

What is the rhythm of GH like?

A

It has pulsatile release with a few pulses a day, most of GH is secreted during sleep.

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9
Q

What can a high GH mean be caused by?

A

Acromegaly.

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10
Q

How does a growth hormone deficiency affect skeletal growth?

A

Leads to short stature in children.

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11
Q

What is secreted form the hypothalamo-pituitary-adrenal axis?

A

CRH and ACTH in a pulsatile function.

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12
Q

What changes release amount of CRH and ACTH?

A

Positive hypothalamic control affects CRH and stress can causes ACTH release.

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13
Q

How does the rhythm of the ACTH axis vary throughout the day?

A

Increased early in the morning, decreased in the evening.

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14
Q

What does the pituitary-gonadal axis secrete?

A

LH and FSH.

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15
Q

How does the pituitary gonadal axis get controlled in men?

A

Simple negative feedback. LH drives testosterone secretion and FSH drives sperm production.

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16
Q

How does the pituitary gonadal axis get controlled in women?

A

In follicular phase, LH pulses cause release of oestrogen. In mid to late luteal phase LH pulses cause progesterone release. There is positive feedback during mid cycle LH/FSH surge.

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17
Q

What does the pituitary thyroid axis regulate?

A

TRH stimulates the pituitary to secrete TSH into circulation. TSH activates follicular cells in the thyroid to produce T3 and T4. It’s controlled by negative feedback.

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18
Q

What is primary gland failure in the pituitary-thyroid axis?

A

When the thyroid gland doesn’t secrete T3/4. This means T3/4 levels drop, stimulating the pituitary and hypothalamus as part of the negative feedback cycle. So TRH and TSH levels rise but T3/4 levels remain low.

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19
Q

What is secondary gland failure in the pituitary-thyroid axis?

A

When the pituitary gland doesn’t work to release TSH. This leads to low secretion of T3/4 from the thyroid so both the end organ hormone and pituitary hormone are low.

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20
Q

How does excess hormone production by the primary gland affect the pituitary-thyroid axis?

A

It means more T3/4 is secreted from the thyroid gland so there is a negative feedback that inhibits secretion from the pituitary and hypothalamus. So TSH levels fall and the end organ hormone is high but the pituitary hormone is low.

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21
Q

How does excess hormone production by the pituitary gland affect the pituitary-thyroid axis?

A

Means more TSH is secreted, which increases T3/4 secretion from the thyroid. So end organ hormones and pituitary hormones are high.

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22
Q

What does the lactotroph axis control?

A

The levels of prolactin, which initiate and maintain lactation.

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23
Q

How is prolactin secretion controlled?

A

Under tonic inhibitory control by dopamine, minor positive control by TRH and positive control from oestrogen. It has pulsatile secretion, levels are higher at night.

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24
Q

What are five causes of high prolactin levels?

A

Pregnancy, physiological stress, pharmacological reasons (dopamine antagonists), pituitary tumours or prolactinoma, or polycyclic ovaries.

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25
Q

How is ADH secretion from the posterior pituitary controlled with high blood osmolality?

A

Osmoreceptors detect the high blood concentration and trigger release of ADH so more water gets recycled into the blood stream and blood osmolality is stabilised.

26
Q

What is diabetes insipidus?

A

An ADH deficiency or resistance. It means water can’t be reabsorbed by the kidney, causing polyuria and polydipsia. It also leads to high serum osmolality and low urine osmolality.

27
Q

What is cranial diabetes insipidus a disease of?

A

Disease of hypothalamus or pituitary stalk and caused by ADH deficiency.

28
Q

How can pituitary diseases present?

A

Compression of local structure and abnormal pituitary function.

29
Q

What is optic chiasm compression caused by in the pituitary?

A

Posterior extension of a pituitary gland tumour.

30
Q

What can cavernous sinus invasion of the pituitary cause?

A

Cranial nerve palsies.

31
Q

Which of the five hormones secretes by the anterior pituitary are controlled by:

a. Positive control?
b. Negative control?

A

a. GH, LG/FSH, TSH and ACTH

b. Prolactin.

32
Q

What affect will an anterior pituitary tumour have on hormone levels?

A

GH, LH/FSH, TSH and ACTH will go down. Prolactin will increase.

33
Q

What are clinical features of hypopituitarism?

A

Poor growth in children, loss of body hair, lethargic and pallor.

34
Q

What are the clinical features of diabetes insipidus?

A

Polyuria, polydipsia, dilute urine and concentrated blood.

35
Q

What are prolactinomas?

A

Prolactin-secreting pituitary tumours.

36
Q

What do prolactinomas cause?

A

Menstrual disturbance, galactorrhoea (milk coming from breasts outside of pregnancy) and infertility.

37
Q

How do prolactin levels differ with a macroprolactinoma and a microprolactinoma?

A

Macroprolactinomas have prolactin levels of above 5000 mU/l whereas microprolactinomas have prolactin levels of 2100mU/l. The normal range is 50-400mU/l.

38
Q

What does a non-functioning adenoma cause?

A

High prolactin due to loss of prolactin inhibition. Levels are not as high as with prolactinomas.

39
Q

How are macroprolactinomas treated?

A

Using dopamine agonists.

40
Q

How are non-functioning adenomas treated?

A

Using surgery if compressive symptoms.

41
Q

What is acromegaly caused by?

A

GH secreting pituitary tumour.

42
Q

What are the clinical presentations of acromegaly?

A

Growth of hands and feet, coarse features, sweating, headaches, hypertension and diabetes. There is reversible swelling of the soft tissues but the bone growth is not reversible.

43
Q

What does acromegaly before puberty cause?

A

Gigantism.

44
Q

What is Cushing’s disease caused by?

A

ACTH secreting pituitary tumour.

45
Q

What are the clinical presentations of Cushing’s disease?

A

Rounded and plethoric face, central obesity with striae, easy bruising, proximal myopathy, hypertension and diabetes.

46
Q

What can cause pseudocushing’s?

A

Alcohol and steroids.

47
Q

What do TSHomas cause?

A

High T3/4 and high TSH.

48
Q

What are gonadotropinomas and what do they cause?

A

They’re LH/FSH secreting pituitary tumours TATA cause high LH/FSH and high sex steroids.

49
Q

What are the endocrine tests used for pituitary diseases?

A

Basal and dynamic.

50
Q

When should basal pituitary tests be done?

A

For hormones that are stable at any time of the day.

51
Q

When should dynamic tests be used?

A

With pulsatile hormones. If a deficiency is suspected, then stimulate the gland. If an excess is suspected, then try to suppress the gland.

52
Q

How should insulin tolerance tests be conducted?

A

Induce hypoglycaemia, this is unpleasant and causes hot Adam sweaty feelings, tachycardia and faint feeling. More GH should be released, so this tests for deficiency. It also checks for ACTH reserves.

53
Q

What can glucose tolerance tests help diagnose expect diabetes?

A

Acromegaly, if there is a failure to suppress GH levels, then it suggests acromegaly.

54
Q

When is an ACTH stimulation test performed?

A

When there is a suspected ACTH deficiency due to isolated or hypopituitarism.

55
Q

What can too much ACTH in a glucose suppression test suggest?

A

Cushing’s syndrome.

56
Q

What can a dexamethasone suppression test be used to detect?

A

Acromegaly if cortisol levels aren’t low.

57
Q

How can pituitary diseases be treated?

A

Control or removal of tumour, reduction of excess hormone secretion or replacement of hormone deficiencies.

58
Q

How can a pituitary tumour size be controlled?

A

Surgery - transsphenoidal (through nose) or trans cranial.
Radiotherapy - external beam or gamma knife.
Medical therapy - dopamine agonists, somatostatin analogues or GH receptors antigonists.

59
Q

What are the advantages of radiotherapy on pituitary tumours?

A

Prevention of tumour growth and protection of vision.

60
Q

What are disadvantages of radiotherapy in pituitary tumour treatment?

A

Damage to normal pituitary gland and possible increased risk of stroke.

61
Q

What is somatostatin used to treat?

A

Acromegaly by monthly injections

62
Q

What tissues are the anterior and posterior pituitary made of?

A

Anterior - primitive gut tissue

Posterior - brain tissue.

4. Metabolism (22 decks)

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