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PATH 406 > Pituitary > Flashcards

Pituitary Flashcards

1
Q

Where is the pituitary gland located? How is it divided?

A

Hypothalamus
Anterior and posterior pituitary

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2
Q

How are the anterior pituitary hormones regulated?

A
  1. Secretion of hypothalamic hormones is influenced by higher centres in the brain
  2. Hypothalamic hormones reach the anterior pituitary through a series of portal BVs
  3. Secretion of anterior pituitary hormones are controlled by the hypothalamic hormones
  4. Secretion of both anterior pituitary and hypothalamic hormones are regulated by negative feedback from the target organ hormones
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3
Q

What are the types of pituitary tumors?

A

Non-functional (30%) or functional

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4
Q

What are the hormones secreted in functional tumors based on frequency?

A

Prolactin
Growth hormone
ACTH
TSH/LH/FSH

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5
Q

What are microadenomas and macroadenomas?

A

Microadenomas are tumours <10 nm, macroadenomas are larger tumours

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6
Q

What are the symptoms of pituitary tumours?

A
  1. If functional, excess secretion of one or more hormone
  2. Hypopituitarism
    - hypofunction of other pituitary hormones
  3. Diabetes insipidus
    - tumour extension into posterior pituitary
  4. Mass effects - papilledema
  5. Visual field defects
    - Impinge on optic chiasm
    - Leads to bitemporal hemianopia
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7
Q

What is a good way to a) see bony structures around pituitary, and b) visualize soft tissue?

A

a) CT
b) MRI

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8
Q

If there is a deficiency of an anterior pituitary hormone, what test do we use to confirm this?

A

Hormone stimulation test

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9
Q

If there is an excess of an anterior pituitary hormone, what test do we use?

A

Hormone suppression test

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10
Q

What hormone released by the hypothalamus inhibits:
1. GH
2. Prolactin

A
  1. Somatostatin
  2. Dopamine
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11
Q

What hormone relased by the hypothalamus stimulate:
1. GH
2. ACTH
3. TSH
4. FSH, LH

A
  1. Growth-hormone releasing hormone (GHRH)
  2. Corticotropin-releasing hormone (CRH)
  3. Thyrotropin-releasing hormone (TRH)
  4. Gonadotropin-releasing hormone (GnRH)
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12
Q

What is the function of growth hormone? What is the effect of GH?

A

Function - stimulate the liver to produce insulin-like growth factor 1 (IGF-1)

Effect
1. Incr cell growth + proliferation
2. Incr bone growth
3. Incr muscle mass

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13
Q

What is GH secretion stimulated by? What is it inhibited by?

A

Stimulated
1. Sleep
2. Exercise
3. Stress
4. Fasting, hypoglycemia
5. Ingestion of certain aa

Inhibited - increase in plasma glucose

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14
Q

What is gigantism?

A

A GH excess disorder that occurs in childhood before the epiphyses have fused

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15
Q

What is acromegaly?

A

When excess GH occurs in adulthood

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16
Q

What are the clinical features of acromegaly?

A
  1. Acromegalic facies
  2. Excess sweating
  3. Large hands/feet
  4. Cardiomegaly
  5. Hypertension
17
Q

What are the clinical features of GH excess?

A
  1. Glucose intolerance (insulin resistance)
  2. Hyperprolactinemia - from stalk effect of tumour (remove dopamine inhibition), or prolactin co-secretion (less common)
  3. Visual field defects
  4. Hypopituitarism
  5. Diabetes insipidus
18
Q

What are the investigations for GH excess?

A
  1. Plasma IGF-1 levels
  2. Confirm with glucose suppression test
    - GH > 0.5 ug/L = GH excess
19
Q

What is the pro and con for measuring plasma IGF-1 levels?

A

Pro - less fluctuation than GH
Con - affected by age, nutritional status, liver fcn

20
Q

What is the treatment for GH excess?

A
  1. Surgery
  2. External irradiation
  3. Medical therapy
    - Somatostatin analogues
    - Dopamine antagonists
    - GH receptor antagonist
  4. Hormonal replacement therapy if hypopituitarism
21
Q

What are the clinical features of GH deficiency in children and adults?

A

Children
- Slow growth but normal body proportions

Adults
- Fatigue
- Decr. muscle bulk/strength
- Decr. bone density
- Incr. abdominal fat, total choleserol + LDL-C = incr. CV risk

22
Q

What are the investigations for GH deficiency?

A
  1. Plasma IGF-1 levels
  2. Confirm with insulin hypoglycemia test
    - If GH < 5 = GH deficiency

Alternative stimuli = arginine, glucagon, L-dopa

23
Q

What is the treatment for GH deficiency?

A
  1. Regular synthetic human GH injections
  2. Monitor with IGF-1 levels
24
Q

When is prolactin released?

A
  1. Sleep
  2. After meals
  3. After exercise
  4. During pregnancy
  5. With suckling
  6. Stress
25
Q

What is the secretion of prolactin regulated by?

A

Dopamine from the hypothalamus (inhibitory)

26
Q

What is prolactin deficiency?

A

Failure of lactation

27
Q

What are the clinical features of prolactin excess?

A

Excess prolactin inhibits GnRH = decr. in LH/FSH = leads to:

Males
1. Decr. testosterone production
2. Decr. spermatogenesis = infertility

Females
1. Decr. ovulation = menstrual irregularities, infertility
2. Galactorrhea

28
Q

What are the causes of prolactin excess?

A
  1. Pregnancy
  2. Estrogen
  3. Prolactinoma
  4. Macroprolactin
29
Q

What is macroprolactin? How to investigate for the presence of macroprolactin?

A

Complex of PRL and IgG Ab

Confirmed by measuring prolactin after precipitation of macroprolactin present with polyethylene glycol (PEG)

30
Q

What is the treatment for PRL excess?

A

1st line treatment - dopamine agonist

If doesn’t work - surgery

Last choice - external radiotherapy

31
Q

What is the order of pituitary hormones loss?

A

Go Look For The Adenoma Please!
1. GH
2. LH
3. FH
4. TSH
5. ACTH
6. PRL

32
Q

What are the clinical features of hypopituitarism?

A

GH - GH deficiency
ACTH - secondary adrenal deficiency
TSH - secondary hypothyroidism
FSH, LH - secondary hypothyroidism
PRL - Lactation failure
ADH - Diabetes insipidus

33
Q

What hormones must be replaced in patients with hypopituitarism?

A
  1. Glucocorticoids
  2. Thyroxine

PATH 406 (24 decks)

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