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Metabolism, Endocrinology and Haematology > HPA Axis and Growth Hormone > Flashcards

HPA Axis and Growth Hormone Flashcards

1
Q

Where is the pituitary gland located

A

Beneath the hypothalamus in the sella turcica

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2
Q

Where do the two lobes of the pituitary gland originate from

A

Anterior - projection of ectoderm, upwards from roof of mouth

Posterior - from ectodermal tissue, growing downwards from diencephalon of developing brain

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3
Q

Where do axons from the hypothalamus travel down to reach the pituitary

A

Infundibulum - pituitary stalk

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4
Q

What are the two posterior pituitary hormones and where are they produced (exact sites)

A

Oxytocin (OT) and Antidiuretic hormone (ADH)

Synthesised by neurones in supraoptic and paraventricular nuclei of hypothalamus

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5
Q

What stimulates oxytocin release

A

Suckling in milk let-down reflex

Stimulus of pressure on cervix and uterine wall during childbirth

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6
Q

What are the roles of oxytocin

A

Cause mammary alveoli to contract to squeeze milk out of them into duct system

Initaites powerful uterine contractions - stimulates uterine smooth muscle cells

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7
Q

What stimulates ADH release

A

Changes in plasma osmolality - increase will cause more to be released

Haemorrhage will cause ADH to be released

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8
Q

What does ADH cause

A

Increases permeability of collecting ducts (distal tubule) to water to increase reabsorption of water

Acts on smooth muscle cells of blood vessels to cause vasoconstriction

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9
Q

Where are tropic hormones produced by the hypothalamus stored

A

Median eminence above anterior pituitary

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10
Q

What 7 tropic hormones are produced by the hypothalamus

A

TRH - thyrotropin releasing hormone

PRH - prolactin releasing hormone

PIH - prolactin release-inhibiting hormone (dopamine)

CRH - corticotropin releasing hormone

GnRH - gonadotropin releasing hormone

GHRH - growth hormone releasing hormone

GHIH - growth hormone inhibitory hormone (somatostatin)

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11
Q

What hormones are secreted by the anterior pituitary and what hormones stimulate and inhibit this release

A

Thyroid stimularing hormone - Stim: TRH, Inhib: GHIH

Prolactin - Stim: PRH/TRH, Inhib: PIH and GHIH

Adrenocorticotropin hormone - Stim: CRH

Growth hormone - Stim: GHRH, Inhib: GHIH

Luteinising hormone - Stim: GnRH

Follicle stimulating hormone - Stim: GnRH

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12
Q

What is somatotropin, where is it produced and what stimulates and inhibits its production

A

Polypeptide hormone produced by somatotrope cells in anterior pituitary

Simt: GHRH

Inhib: somatostatin/GHIH

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13
Q

What does GH stimulate the release of and where from

A

Insulin like growth factors (IGFs) - somatomedins

Released by cells in liver and skeletal muscle

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14
Q

What are the actions of GH and IGFs

A

GH - IGF production, stimulation of long bone growth

IGFs - cause muscle hypertrophy, stimulate bone and cartilage growth

GH and IGFs - help maintain muscle and bone mass in adults, promote healing and tissue repair as well as modulate metabolism

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15
Q

How is GH secretion metabolically regulated

A

Decrease in glucose or free fatty acid increases GH secretion

Increase in glucose or free fatty acid decreases GH secretion

Fasting increases GH secretion

Obesity decreases GH secretion

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16
Q

How is GH secretion regulated by the CNS

A

Deep sleep causes surge in GH secretion

Light sleep inhibits GH secretion

Stress increases GH secretion

Exercise increases GH secretion

17
Q

What are the long and short loop mechanisms in GH secretion regulation

A

Long loop - IGFs inhibit GHRH release, IGFs stimulate somatostatin release, IGFs inhibit GHRH action

Short loop - GH stimulates somatostatin release

18
Q

How does GH exert its effect on cells

A

Binds to GH receptor - type of cytokine receptor

Receptor is coupled to Janus kinase and one of its effects is to turn on production of IGFs - mainly IGF-1

IGF-1 activates IGF receptors on target cells

Other GH effects include activation of signalling pathways

19
Q

What effects does IGF-1 mediate in an adult body

A

Hypertrophy

Hyperplasia

Increase in rate of protein synthesis

Increase in rate of lipolysis in adipose tissue

Decrease in glucose uptake

20
Q

What does a deficiency of GH cause

A

In childhood results in pituitary dwarfism

Responds to GH therapy, get normal growth

21
Q

What does an excess of GH cause

A

In children causes gigantism

In adults causes acromegaly

22
Q

What other hormones influence growth

A

Insulin

Thyroid hormones

Androgens

Estrogens

Glucocorticoids

Metabolism, Endocrinology and Haematology (27 decks)

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