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R - Endocrine Physiology (Megan) > Lecture 4 - Growth and disorders > Flashcards

Lecture 4 - Growth and disorders Flashcards

1
Q

Which factors affect growth?

A

Genetics
Nutrition
Hormones

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2
Q

What factor influences growth the most?

A

Hormones (even if genetics and nutrition are good)

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3
Q

Which hormones have a permissive effect on growth hormone?

A

Growth hormone releasing hormone
Thyroid hormone
Insulin
Sex hormones (oestrogen + testosterone).

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4
Q

Which hormone has an antagonistic effect on growth hormone?

A

Growth hormone inhibiting hormone (Somatostatin)

Cortisol

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5
Q

Which hormone does growth hormone use to act indirectly on the body?

A

IGF-1

insulin like growth factor 1.

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6
Q

What two hypothalamic hormones dictate growth hormone release?

A

Somatostatin (GHIH) and GHRH.

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7
Q

What periods of life are rapid growth periods?

A

Infancy (in utero and the first 10 months post utero).

Puberty.

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8
Q

When does growth hormone play a role in growth?

A

After 10 months - for the rest of your life.

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9
Q

What type of growth do sex hormones promote?

A

Elongation of long bones (from the epiphyseal plate).

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10
Q

What hormones terminate growth?

A

The same sex hormones at the end of puberty. (late teens/early 20s).

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11
Q

What causes growth in puberty?

A

The sex hormones - these promote the release of more GH and IGF-1

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12
Q

Which hormones are responsible for infancy growth?

A

Nutrition from mother
Thyroid hormone
Insulin

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13
Q

What type of bone growth still happens after puberty?

A

Remodelling of bones - like membranous bones (skull, jaw etc)

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14
Q

Who usually hits their puberty growth spurt first?

A

Girls

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15
Q

Which hormones are responsible for the increase in GH in puberty?

A

The sex hormones - testosterone and oestrogen

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16
Q

What is seen in babies who lack GH and IGF-1?

A

They are born normal size (these hormones don’t become important in growth until later)

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17
Q

What is seen in babies who lack GH and IGF-1?

A

They are born normal size (these hormones don’t become important in growth until later)
They fail to grow normally after 10 months

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18
Q

Which hormone is critical for brain development?

A

Thyroid hormone

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19
Q

What is seen in hypothyroid babies?

A

Often nothing at first (they get their thyroid from the mother)
After birth, they fail to develop cognitively and growth

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20
Q

What happens in children deficient in growth hormone?

A

They are short, but normal cognitively and in proportion.

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21
Q

What happens in children with a thyroid deficiency?

A

Normal at birth - due to getting thyroid in utero from mother
They are short (thyroid has a permissive effect on growth hormone)
They have poor cognitive development
They retain infantile features (struggle to move fat deposits)

22
Q

When is IGF-II used?

A

In utero

23
Q

Where is IGF-I used?

A

After birth

24
Q

What is iodine needed for?

A

The production of thyroid hormone

25
Q

What occurs in maternal iodine deficiency?

A

This is very rare. Causes severe growth retardation intra-uterine because thyroid cannot be made (mum can’t pass on to baby).

26
Q

What happens with a lack of GH?

A

They appear normal at birth.
Stunted growth - but still proportionate
don’t retain infantile features
normal cognitive function

27
Q

What is another name for Growth Hormone?

A

Somatotropin

28
Q

What is another name for growth hormone inhibiting hormone?

A

Somatostatin

29
Q

Where is somatotropin released from?

A

Somatotroph cells in the anterior pituitary.

30
Q

What controls the ratio of GHIH and GHRH?

A

Factors which influence the hypothalamus

31
Q

Can growth hormone act on its own?

A

It will produce stunted growth, even if there’s lots of it. If there is no thyroid hormone or insulin.

32
Q

What is GH used for after puberty?

A

Remodelling and maintenance/repair of bones.

It promotes an increase in cell size and cell division.

33
Q

What receptors does growth hormone act on?

A

Tyrosine kinase

34
Q

What direct effects does GH have?

A
  • Increases blood glucose
  • increasing lipolysis (fatty acids made into ketone bodies)
  • increases amino acid uptake
  • antagonistic effect against insulin to prevent muscle and adipose taking up all glucose
35
Q

What is another name for IGF-1?

A

somatomedin C

36
Q

What type of hormones are GH and IGF-1?

A

Peptides BUT they are carried through the plasma bound to carrier proteins

37
Q

Why is Gh and IGF-1 bound to carrier proteins?

A

To provide a reservoir and stop erratic spikes in the blood of secretion.
Extends the half life - protects against excretion from the urine.

38
Q

What is IGF-1 responsible for?

A

promotion of cartilage growth and the elongation of long bones

39
Q

When is most GH secreted?

A

In puberty
During the first 2 hours of sleep (deep delta sleep)
because general energy levels are low, so the glucose in the blood can be used almost entirely for growth

40
Q

When is IGF-1 released?

A

IGF-1 levels are constant because it binds tightly to the carrier protein. - less vulnerable to degradation - long half-life.
gives a constant increase in growth and not just in the first 2 hours of sleep.
there’s not big spikes like seen in GH.

41
Q

What is the half life of GH?

A

20 mins

42
Q

What is the half life of IGF-1?

A

20 hours

43
Q

Stimuli causing an increase in GHRH - so increase in GH?

A
  • decrease in energy supply to cells
  • increased amino acid levels in plasma
  • physical stress and illness (due to increase in energy supply BUT growth might be stunted because cortisol is also there)
  • increase in delta sleep
  • sex hormones (oestrogen and testosterone - they increase GH directly not GHRH first)
44
Q

Stimuli causing increase in GRIH - so decrease in GH?

A
  • hyperglycaemia
  • high levels of free fatty acids
  • ageing (this is why tissue repair is less efficient in older people)
  • cortisol
45
Q

What is gigantism?

A

Increase in GH from a pituitary tumour BEFORE the epiphyseal plate closes.
Extra elongation of long bones.

46
Q

What is acromegaly?

A

Increase in GH from a pituitary tumour AFTER the epiphyseal plate closes.
No longitudinal growth and no increase in height BUT increase in width.

47
Q

What is the common sign of acromegaly?

A

Increase in feet size of adults.

48
Q

What is treatment for gigantism or acromegaly?

A

Remove the pituitary tumour by surgery or use GHIH.

49
Q

What is a common symptom of a pituitary tumour?

A

Bitemporal hemianopia (pressure on optic chiasm).

50
Q

What is hypo secretion or hyporesponsiveness caused by?

A

gives abnormally small stature.

  • GHRH deficiency (hypothalamus problem)
  • GH deficiency (pituitary problem)
  • under expression of GH receptor
  • precocious puberty (sex hormones released too early and growth stopped too soon)
  • reduce in thyroid (loss of permissive effect)
51
Q

Whatis precocious puberty?

A

excess release of gonadotropin releasing hormone. - increase in sex hormone - earlier closure of epiphyseal growth plate.

52
Q

What is gestational diabetes?

A

women gets diabetes when pregnant.
High blood glucose levels travel to baby.
Baby uses the extra glucose and is born very large.

R - Endocrine Physiology (Megan) (10 decks)

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