Lecture 4 - Growth and disorders

Question 1

Which factors affect growth?

Answer 1

Genetics
Nutrition
Hormones

Question 2

What factor influences growth the most?

Answer 2

Hormones (even if genetics and nutrition are good)

Question 3

Which hormones have a permissive effect on growth hormone?

Answer 3

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

Question 4

Which hormone has an antagonistic effect on growth hormone?

Answer 4

Growth hormone inhibiting hormone (Somatostatin)

Cortisol

Question 5

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

Answer 5

IGF-1

insulin like growth factor 1.

Question 6

What two hypothalamic hormones dictate growth hormone release?

Answer 6

Somatostatin (GHIH) and GHRH.

Question 7

What periods of life are rapid growth periods?

Answer 7

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

Puberty.

Question 8

When does growth hormone play a role in growth?

Answer 8

After 10 months - for the rest of your life.

Question 9

What type of growth do sex hormones promote?

Answer 9

Elongation of long bones (from the epiphyseal plate).

Question 10

What hormones terminate growth?

Answer 10

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

Question 11

What causes growth in puberty?

Answer 11

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

Question 12

Which hormones are responsible for infancy growth?

Answer 12

Nutrition from mother
Thyroid hormone
Insulin

Question 13

What type of bone growth still happens after puberty?

Answer 13

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

Question 14

Who usually hits their puberty growth spurt first?

Answer 14

Girls

Question 15

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

Answer 15

The sex hormones - testosterone and oestrogen

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

Which hormone is critical for brain development?

Answer 18

Thyroid hormone

Question 19

What is seen in hypothyroid babies?

Answer 19

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

Question 20

What happens in children deficient in growth hormone?

Answer 20

They are short, but normal cognitively and in proportion.

Question 21

What happens in children with a thyroid deficiency?

Answer 21

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)

Question 22

When is IGF-II used?

Answer 22

In utero

Question 23

Where is IGF-I used?

Answer 23

After birth

Question 24

What is iodine needed for?

Answer 24

The production of thyroid hormone

Question 25

What occurs in maternal iodine deficiency?

Answer 25

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

Question 26

What happens with a lack of GH?

Answer 26

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

Question 27

What is another name for Growth Hormone?

Answer 27

Somatotropin

Question 28

What is another name for growth hormone inhibiting hormone?

Answer 28

Somatostatin

Question 29

Where is somatotropin released from?

Answer 29

Somatotroph cells in the anterior pituitary.

Question 30

What controls the ratio of GHIH and GHRH?

Answer 30

Factors which influence the hypothalamus

Question 31

Can growth hormone act on its own?

Answer 31

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

Question 32

What is GH used for after puberty?

Answer 32

Remodelling and maintenance/repair of bones. | It promotes an increase in cell size and cell division.

Question 33

What receptors does growth hormone act on?

Answer 33

Tyrosine kinase

Question 34

What direct effects does GH have?

Answer 34

- 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

Question 35

What is another name for IGF-1?

Answer 35

somatomedin C

Question 36

What type of hormones are GH and IGF-1?

Answer 36

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

Question 37

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

Answer 37

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

Question 38

What is IGF-1 responsible for?

Answer 38

promotion of cartilage growth and the elongation of long bones

Question 39

When is most GH secreted?

Answer 39

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

Question 40

When is IGF-1 released?

Answer 40

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.

Question 41

What is the half life of GH?

Answer 41

20 mins

Question 42

What is the half life of IGF-1?

Answer 42

20 hours

Question 43

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

Answer 43

- 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)

Question 44

Stimuli causing increase in GRIH - so decrease in GH?

Answer 44

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

Question 45

What is gigantism?

Answer 45

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

Question 46

What is acromegaly?

Answer 46

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

Question 47

What is the common sign of acromegaly?

Answer 47

Increase in feet size of adults.

Question 48

What is treatment for gigantism or acromegaly?

Answer 48

Remove the pituitary tumour by surgery or use GHIH.

Question 49

What is a common symptom of a pituitary tumour?

Answer 49

Bitemporal hemianopia (pressure on optic chiasm).

Question 50

What is hypo secretion or hyporesponsiveness caused by?

Answer 50

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)

Question 51

Whatis precocious puberty?

Answer 51

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

Question 52

What is gestational diabetes?

Answer 52

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