Normal Growth and Clinical Aspects

Question 1

How is growth regulated ?

Answer 1

Growth hormone release from ant. pituitary, Thyroid hormone, insulin, sex steroids, stress, genetics

Question 2

Where is GH released from?

Answer 2

The anterior pituitary

Question 3

Where is GHIH and GHRH released from?

Answer 3

They hypothalamus

Question 4

What is the action of growth hormone?

Answer 4

Growth and Development (indirect), Regulation of Metabolism (direct)

Question 5

When does GH take over the role of Growth in humans?

Answer 5

around 8-10 months of age

Question 6

What conditions must be present for GH to stimulate growth?

Answer 6

GH requires permissive action of thyroid hormones and insulin

Question 7

How is the growth effect of GH mediated?

Answer 7

Through stimulation of cell size and cell division in its many target tissue

Question 8

What intermediate mediates the action of GH?

Answer 8

IGF-1

Question 9

Where is IGF-1 secreted?

Answer 9

The liver

Question 10

How does IGF-1 mediate GH?

Answer 10

Through a negative-feedback loop via inhibiting GHRH and stimulating GHIH

Question 11

How does GH/IGF-I affect bone growth?

Answer 11

GH stimulates chondrocyte precursor cells in epiphyseal plates to differentiate into chondrocytes.

During differentiation, cells begin to secrete IGF-1 and respond to IGF-1

IGF-1 then acts as an autocrine or paracrine agent, stimulating the differentiation of chondrocytes to divide and produce cartilage

Question 12

When do epiphyseal plates close?

Answer 12

During adolescence under the influence of sex hormones

Question 13

What are the direct effects of GH?

Answer 13

Increases gluconeogenesis, reduces the ability of insulin to uptake glucose, makes adipocytes sensitive to lipolytic stimuli, increases muscle, liver and adipose tissue amino acid uptake and protein synthesis

Question 14

What stimulates GHRH secretion?

Answer 14

Actual or potential decrease in energy supply to cells, increased amounts of amino acids in plasma, stressful stimuli, delta sleep, oestrogen and androgens

Question 15

What stimulates GHIH?

Answer 15

Glucose, FFA, REM Sleep, Cortisol

Question 16

What affects growth?

Answer 16

Hormones
Nutrition
Genetics

Question 17

What hormones affect growth?

Answer 17

GH, IGF-I, Thyroid Hormones, Androgens, Oestrogens, Glucocorticoids and Insulin

Question 18

What is cretinism?

Answer 18

A condition where children are hypothyroid from birth. Results in retardation of growth and retain infantile facial features

Question 19

How does cretinism affect GH levels?

Answer 19

It doesn’t. GH levels are normal

Question 20

Name the two periods of rapid growth in humans?

Answer 20

Infancy and Puberty

Question 21

How many times do infants grow on average ?

Answer 21

Growth spurts of around 2.5 cm in a few days then nothing

Question 22

What is growth like during puberty?

Answer 22

Androgens and oestrogens produce GH spikes that increase IGF-1 which increases growth

Question 23

What is gigantism?

Answer 23

excess GH due to a pituitary tumour before epiphyseal plates of long bones close = excessive growth

Question 24

Define acromegaly

Answer 24

Excess GH due to a pituitary tumour after epiphyseal plates have sealed. Long bones cannot increase so no increase in height but can have enlarged hands and feet

Question 25

What may contribute to dwarfism?

Answer 25

A deficiency in GHRH, Abnormal GH secreting cells, End organ unresponsive to GH, Genetic mutation, Precocious Puberty, Hypothyroid Children