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MEH > HPA Axis and Growth Hormone > Flashcards

HPA Axis and Growth Hormone Flashcards

1
Q

What is the Hypothalamic Pituitary Axis?

A

A complex functional unit formed from Hypothalamus and Pituitary gland, serving as a major link between endocrine and nervous systems

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2
Q

Describe where the Pituitary gland is located, in reference to the hypothalamus

Why is the posterior pituitary gland not a proper gland?

A

Beneath hypothalamus in a socket of bone called the Sella Turcica

Post. pituitary gland is not a proper gland, as it doesn’t make its own hormones

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3
Q

Name 6 processes controlled by the HPA Axis

A 
Body growth 
Water homeostasis 
Puberty 
Adrenal and Thyroid gland function
Lactation
Reproduction
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4
Q

Compare the embryological origins of the 2 pituitary gland parts?

What are the 2 parts also called?

A

Anterior: Adenohypophysis
- Evagination from oral ectoderm, Rathke’s Pouch (primitive gut tissue)

Posterior: Neurohypophysis
- Originates from neuroectoderm (Primitive brain tissue)

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5
Q

How is the posterior pituitary gland physically connected to the Hypothalamus?

A

Hypothalamus drops down through Infundibulum to form the Posterior Pituitary gland

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6
Q

Outline the pathway of Oxytocin and ADH from production to secretion

What kind of signalling is this?

A
  1. ADH and Oxytocin produced by neurosecretory cells in Supraoptic and Paraventricular nuclei of hypothalamus, respectively
  2. Transported down axons to Posterior Pituitary
  3. Stored and released from posterior pituitary into general circulation (Blood)

Neurocrine signalling

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7
Q

The posterior pituitary gland RELEASES ADH and Oxytocin, but doesn’t produce them.

How is the release regulated

A

Regulated by neuronal inputs to hypothalamus

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8
Q

Outline the pathway of Anterior Pituitary Hormones from production to secretion

What kind of signalling is this?

A
  1. Made in hypothalamus, transported down axons
  2. Stored in median eminence before release into Hypophyseal Portal System
  3. These hormones stimulate/ inhibit Target Endocrine Cells in Anterior Pituitary Gland
  4. Endocrine cells of anterior pituitary gland secrete hormones into blood

Neurocrine signalling

((Anterior pituitary hormones also affect neighbouring cells)(Autocrine and Paracrine)

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9
Q

Name 2 functions of Oxytocin and 1 function of ADH

A

ADH;
- Regulation of water body volume

Oxytocin;

  • Milk let down
  • Uterus contractions during birth
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10
Q

Name the 8/9 hormones made in the Hypothalamus

Which ones are Tropic hormones?
Which ones are released from posterior pituitary?

A

Released from posterior pituitary;

  • Oxytocin
  • ADH

Tropic;

  • TRH(Thyrotropin releasing hormone)
  • PIH (Prolactin release-inhibiting hormone)
  • CRH (Corticotropin releasing hormone)
  • GnRH (Gonadotropin releasing hormone)
  • GHRH (Growth hormone releasing hormone)
  • GHIH (Growth hormone inhibiting hormone)
  • PRH (May not exist)
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11
Q

Compare Tropic and Trophic hormones

A

Tropic hormones: Affect release of other hormones

Trophic hormones: Affect growth

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12
Q

What are the proper names of Dopamine and Somatostatin

A

Dopamine: PIH

Somatostatin: GHIH

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13
Q

Name the 6 hormones made in the Anterior Pituitary Gland?

A
  • TSH (Thyroid stimulating hormone)
  • ACTH (Adrenocorticotrophic hormone)
  • LH (Luteinising hormone)
  • FSH (Follicle stimulating hormone)
  • PRL (Prolactin)
  • GH (Growth Hormone)
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14
Q

Which Tropic hormones cause which Anterior pituitary hormones to be made?

A
  • TRH-> TSH
  • CRH-> ACTH
  • GnRH-> LH and FSH
  • TRH/ PRH-> PRL
  • PIH inhibits-> PRL
  • GHRH-> GH
  • GHIH inhibits-> GH
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15
Q

What 4 factors control growth

A
  • Genetics
  • Nutrition
  • Environment
  • Hormones (Growth hormone is most important)
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16
Q

In negative feedback, compare;

  • Ultra short loop
  • Short loop
  • Direct long loop
  • Indirect long loop
A

Ultra-short;
- Hypothalamic Tropic hormone inhibits itself (In an Autocrine/ Paracrine fashion within the hypothalamus)

Short;
- Inhibition/ stimulation of Hypothalamic releasing/ inhibiting hormone, by the Anterior Pituitary hormone (released in response to the Hypothalamic releasing hormone)

Direct Long;
- Final hormone in pathway inhibits production of its respective Anterior Pituitary hormone

Indirect Long;
- Final hormone in pathway inhibits production of its respective Hypothalamic releasing hormone

17
Q

Where is Growth Hormone made?
What stimulates it?
What inhibits it?

A

Made in Anterior Pituitary Gland
Stimulated by GHRH
Inhibited by GHIH (Somatostatin)

18
Q

How are the Growth Hormone’s effects mainly exerted?

How do liver and skeletal muscle cells response to Growth Hormone

A

Via Insulin-like Growth Factors

Liver and skeletal muscle cells produce and secrete IGFs

19
Q

Compare the functions of Growth Hormone and Insulin-like Growth Factors before adulthood

A

GH stimulates long bone growth;

  • Length AND width prior to epiphyseal closure
  • Width ONLY after epiphyseal closure

IGFs stimulate BOTH bone and cartilage growth

20
Q

Compare the functions of Growth Hormone and Insulin-like Growth Factors in adulthood

A

GH and IGFs;

  • Maintain muscle mass
  • Maintain bone mass
  • Promote healing and tissue repair
  • Regulate metabolism and body composition
21
Q

Describe the pattern of Growth Hormone secretion

A

GH secretion occurs in a pulsatilla fashion, with circadian rhythm and maximal release late at night

22
Q

Explain how the following affect Growth Hormone secretion;

  • Deep sleep
  • REM
  • Stress
  • Exercise
  • Drop in glucose/ fatty acids
  • Rise in glucose/ fatty acids
  • Fasting
  • Obesity
A
  • Deep sleep= Surge in GH secretion
  • REM= Decreased GH secretion
  • Stress= Increased GH secretion
  • Exercise= Increased GH secretion
  • Drop in glucose/ fatty acids= Increased GH secretion
  • Rise in glucose/ fatty acids= Decreased GH secretion
  • Fasting= Increased GH secretion
  • Obesity= Decreased GH secretion
23
Q

Describe short loop negative feedback in Growth Hormone secretion

A

GH stimulates the release of Somatostatin (GHIH) from hypothalamus

24
Q

Describe long loop negative feedback in Growth Hormone secretion

A

IGFs;

  • Inhibit release of GHRH from hypothalamus
  • Stimulate release of Somatostatin from hypothalamus
  • Inhibit release of GH from Anterior Pituitary (Direct long loop)
25
Q

What does GH deficiency lead to in children?

Is this due to a complete or partial deficiency?
What are 2 features of this condition?

A

Leads to Pituitary Dwarfism (A proportionate type of dwarfism)

Can be due to complete OR partial deficiency

  • Growth rate slower than expected for age
  • Delayed/ no sexual development during teen years
26
Q

Compare the outcomes of Growth Hormone excess;

  • In adulthood and give 3 signs
  • In childhood (before epiphyseal plates close)
A

In adulthood;

  • GH Excess leads to Acromegaly (Means large extremities)
  • Presents with large hands, feet, lower jaw

In childhood;
- GH Excess leads to Gigantism

27
Q

What is often the cause of GH excess in children leading to Gignatism?

Why is gigantism very rare?

A

Pituitary adenoma

Rarely develops due to early diagnosis and treatment

28
Q

How does GH affect cells?

A
  • GH binds to GH receptors
  • GH receptors activate Janus Kinases
  • Signalling pathways activated
  • Transcription factor activation-> IGF production
29
Q

What are the 2 IGFs made in mammals? What are their main functions?

How do they circulate in the bloodstream?

A
  • IGF2 mainly involved in Fetal Growth
  • IGF1 is the major growth factor in adults

Circulate in blood binded to (binding) proteins (regulating their availability)

30
Q

What are the 3 types of signalling carried out by IGFs?

What receptors do they interact with?

Name 3 things IGFs regulate

A
  • Endocrine
  • Autocrine
  • Paracrine

IGF receptors

IGFs regulate;

  • Cell growth (Hypertrophy)
  • Cell number (Hyperplasia)
  • Increase in rate of protein synthesis
31
Q

Name 1 function of IGF-1, related to cancer

A

In some tissues, IGF-1 inhibits apoptosis

MEH (20 decks)

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