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Endocrinology > Hypothalamus, pituitary and growth hormone > Flashcards

Hypothalamus, pituitary and growth hormone Flashcards

1
Q

What processes does the hypothalamic pituitary axis modulate?

A
  • growth
  • milk secretion
  • lactation
  • adrenal gland function
  • thryoid gland function
  • puberty
  • water homeostasis
  • reproduction
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2
Q

Where does the anterior pituitary gland develop from in embryoloigcal development?

A

primitive gut tissue

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3
Q

Where does the posterior pituitary gland develop from in embryoloigcal development?

A

neuroectoderm

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4
Q

Where does the pituitary gland sit?

A

in a pocket of bone in the skull called the sella turcica

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5
Q

What hormones are released from the posterior pituitary gland on neuronal stimulation from the hypothalamus

A
  • oxytocin

- ADH

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6
Q

Where are ADH and oxytocin initially produced from?

A

the supraoptic and paraventricular nuclei of the hypothalamus.
They then travel down nerve axons to the posterior pituitary where they’re released into blood

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7
Q

What effects do ADH and oxytocin have?

A

ADH: stimulates increased water absorbtion by kidneys
Oxytocin: stimulates release of milk on suckling reflex and contracts uterus during birth

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8
Q

Describe the path of hormones released by the anterior pituitary

A
  • hormones from hypothalamus travel down axons to the median eminence (primary capillary plexus) in the pituitary stalk where they’re released into the portal system
  • They travel through portal system to the anterior pituitary where they activate or inhibit release of other hormones from target cells
  • these other hormones are passes into the general circulation
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9
Q

Which 6 hormones are produced by the hypothalamus and travel to the anterior pituitary?

A
  • Remember PTC tripple G
  • Prolactin release- inhibiting hormone (PIH)
  • Thyrotropin releasing hormone (TRH)
  • Corticotrophin releasing hormone (CRH)
  • growth hormone releasing hormone (GHRH)
  • growth hormone inhibiting hormone (GHIH or somatostatin)
  • gonadrotrophin releasing hormone (GnRH)
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10
Q

What stimulates release of prolactin release inhibiting hormone?

A

dopamine

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11
Q

What 6 hormones are released from the anterior pituitary gland and what stimulates (or inhibits) their release?

A
  • PTA GLF
  • Prolactin (inhibited by PIH, stimulated by TRH)
  • TSH (stimulated by TRH)
  • Adenocorticotropic hormone (by CRH)
  • Growth hormone (stimulated by GHRH, inhibited by GHIH)
  • LH (stimulated by GnRH)
  • FSH ( stimulated by GnRH)
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12
Q

What does TSH do?

A
  • stimulates secretion of thyroid hormone from thyroid gland

- increases metabolic rate

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13
Q

What does Adrenocorticotrophic hormone (ACTH) do?

A
  • stimulates secretion of hormones (mainly cortisol) from the adrenal glands as part of the long term stress response
  • cortisol stimulates gluconeogenesis and other metabolic actions
  • also increase BP by increasing fluid retention
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14
Q

What does prolactin do in the body?

A
  • stimulates mammary glands to develop and also milk secretion
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15
Q

What does LH do?

A
  • travels to gonads

- stimulates ovulation and sex hormone release

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16
Q

What does FSH do?

A
  • travels to gonads and stimulates gamete production
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17
Q

Describe the negative feedback in the hypothalamic- pituitary- adrenal axis?

A
  • CRH causes ACTH release which causes cortisol release

- cortisol inhibits release of CRH and ACTH when its levels become suffienctly high

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18
Q

What does growth hormone release cause in liver and muscle? What effects does this have in adults?

A
  • insulin- like growth factor release
  • GH and IGF help maintain muscle and bone mass and promote healing and repair as well as modulate metabolism and body composition
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19
Q

Why are growth hormone and insulin like growth factor important in children and teens?

A
  • GH promote long bone growth
  • length ways before epiphyseal growth plates fuse
  • width ways after they fuse
  • IGF stimulate both bone and cartilage growth
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20
Q

Why is growth hormone not orally active?

A

because it is a 191 amino acid long poly peptide which would be broken down by proteases in the stomach

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21
Q

What things increase growth hormone release?

A
  • onset of deep sleep
  • stress (trauma, surgery, fever)
  • exercise
  • decrease in glucose of fatty acids
  • fasting
22
Q

What things decrease growth hormone release?

A
  • REM sleep
  • high glucose or fatty acids
  • obesity
23
Q

What substance are produced in the brain during stress and sleep which stimulate GH release?

A
  • serotonin, a- adrenergy- stess
  • dopamine- sleep
  • lead to increased GHRH by hypothalamus and decreased GHIH (somatostain) release by hypothalamus
  • lead to increased GH release from pituitary
24
Q

What substances are produced in the body which inhibit GH release which ARE NOT a part of negative feedback

A
  • B- adrenergy
  • Glucose
  • FFA
25
Q

Describe the short and long loop negative feedbacks of GH release

A
  • short loop: high levels GRHR will inhibit the hypothalamus from secreting more GHRH
    Long loops:
  • GH will inhibit GHRH release
  • insulin like growth hormone (AKA somatomedin) will inhibit GH and GRHR release
26
Q

What is the result of growth hormone deficiency in children?

A
  • pituitary dwarfism
  • a proportionate dwarfism, can be caused by partial or complete loss of GH
  • leads to slow growth and delayed sexual development
27
Q

How can pituitary dwarfism be treated?

A

GH therapy

28
Q

What does excess GH from birth and excess GH of adult onset cause?

A
  • if from birth= giantism

- if aquired as adult= acromegaly

29
Q

What type of receptors do growth hormones bind to, what effects do they have?

A
  • janus kinases

- increase transcription of IGF

30
Q

What type of IGF is present mainly in adults and foetuses?

A

in adults: IGF1

in foetuses: IGF2

31
Q

WHat receptors do IGF exert their effect on?

A

IGF receptors (distinct from GH receptors) and hybrid receptors

32
Q

What effect does activation of a hybrid of IGF1 receptor have?

A
  • partial metabolic effects (mainly by insulin only receptors)
  • mainly mitogenic effects: hypertrophy, hyperplasia, increase protein synthesis increase lipolysis in adipose tissue
33
Q

What is the cause of most pituitary disorders?

A

tumours - mostly benign

34
Q

What effect will a benign pituitary tumour have?

A
  • decreased secretion , vision loss, headaches

- very few will caused hypersecretion

35
Q

What can be tested for in blood to check thryoid, gonadal and prolactin axis??

A

thyroid: fT4, TSH
gonadal: LH, FSH, testosterone, oestradiol
Prolactin: serum prolactin

36
Q

How is the HPA (adrenal) axis tested for to test its funcitoning correctly?

A

need to test cortisol but this changes lots through day so do dynamic test:

  • give insulin to pt and check that ACTH goes up as it should
  • Give steroids (dexamethasone) and check that ACTH goes down
37
Q

How can GH axis be tested for to ensure its functioning correctly?

A
  • give insulin and check GH/ GHRH increases

- give glucose and check that GH decreases

38
Q

What else can be done to check for signs of pituitary tumour?

A
  • MRI
  • vision test- they may have bi- temporal impingement of optic nerves causing loss of vision on outside half of eye (tunnel vision)
39
Q

which hormones will increase and which hormones will decrease in a non functional pituitary tumour?

A
  • blocks hormones moving from hypothalamus to pituitary
  • ADH, GH, LSH, FSH, TSH, ACTH all decrease
  • prolactin increase (under negative control)
40
Q

Which hormones are unlikley and more likely to become deficient in a non functioning pituitary tumour?

A
  • TSH, LH and FSH unlikely to become deficient (but does happen)
  • GH, ACTH, ADH likely to decrease
  • prolactin likely to increase but not more than 5,000
41
Q

What will be the effect to the pt of a non functioning pituitary tumour?

A
  • GH deficient first- leads to lower QoL, depression, shortness in children
  • headaches, tunnel/ double vision, nausia experienced due to impingement on brain
  • gonadotrophin sometimes deficient= loss of periods, loss of pubic hair, low libido, man boobs
  • TSH deficient leads to hypothyroidism
  • ACTH deficient leads to tiresness, dizziness, low BP, low sodium
  • ADH low leading to increased urination and need to drink (often as a result of the inflammation from surgical removal)
  • prolactin high but less than 5,000 leads to erectile dysfunction, hardened breast tissue, light, irregular periods, hypogonadism
42
Q

How is a non funcitonal pituitary tumour treated?

A

surgical removal

43
Q

What is most common cause of prolactin increase over 5,000 and what are symptoms?

A

prolactinoma:

  • amenorrhea
  • hypogonadism (underactive overies and testis)
  • galactorhea (milk discharge from nipples)
  • hardened breast tissue
  • erectile dysfunction
44
Q

other than prolactinoma what else can cause hyperprolactinaemia?

A
  • pregnancy
  • severe stress
  • exersize
  • drugs like antiphycotics and antidepressants
  • sarcoidosis
45
Q

How is hyperprolactinaemia (including due to prolactinoma) treated?

A
  • dopamine receptor agonists- leads to more dopamine so more inhibition of prolactin
  • eg. cabergoline
46
Q

What is the common cause and consequence of GH excess?

A

GH secreting tumours

- usually lead to acromegaly

47
Q

What are symptoms of acromegaly?

A
  • vision loss and headaches common (these tumours usually big)
  • nose broadens, jaw widens,facial features become more coarse, lips becomes thicker, hands and feet enlarge
  • excessive sweating
  • premature CVS death
  • increased colonic tumour risk
  • hypertension and diabetes
  • thyroid cancer
  • sleep aponea
  • back pain, kyphosis
  • skin tags
  • often comes with hyperprolactinaemia and hypopituitarism
48
Q

What is diabetes insipidus?

A
  • excessive urination and need to drink due to ADH deficient
  • eg in hypopituitarism, head injuries ect
49
Q

What is the result of ACTH excess?

A

cushings syndrome

50
Q

How can acromegaly be treated?

A
  • surgical removal or adenoma
  • radiation therapy
  • high levels of dopamine agonists
  • synthetic somatostain (GHIH)
  • GH receptor antagonists like pegvisomant

Endocrinology (7 decks)

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