Hormonal Control of Growth and Development

What secretes growth hormone (GH)?

What inhibits GH?

What does GH promote the synthesis of?

• somatotropic cells in the anterior pituitary

• somatostatin

• IGF-1

What is the release of GH like?

When is GH secreted the most?

• irregular and pulsatile

• at night during deep sleep, secretion highest in children especially during puberty

What is height determined by?

• bone growth

How do bones grow?

When do bones stop growing?

• Bone tissue added to region of bone called epiphyseal growth plate

• when the epiphyseal growth plate closes

What do chondrocytes do?

What do osteoblasts do?

• add cartilage to epiphyseal growth plate

• convert the cartilage into bone

What IGF-1 good at?

• promoting cell growth and cell division throughout the body

What is kisspeptin important for?

• the onset of puberty

What are the primary reproductive called?

• gonads - testes and ovaries

What hormones are secreted by gonads?

• testosterone, dihydrotestosterone, oestrogen, progesterone

What does LH do in males?

• reaches Leydig cells where it causes testosterone release

• this results in secondary sexual characteristics and accessory structures

What does FSH do in males?

• FSH reaches Sertoli cells which → spermatogenesis and inhibin

How does the menstrual cycle work?

• FSH and LH stimulate oestrogen release from ovarian follicles

• one follicle becomes dominant and secretes a high levels of oestrogen… this surge in oestrogen exerts positive feedback resulting in high levels of LH and FHS

• surge in LH = ovulation

• Corpus luteum forms and secretes high amounts of oestrogen and progesterone

• -ve feedback by the combination of oestrogen and progesterone lead to low FSH and LH levels

• If pregnancy doesnt occur the corpus luteum degrades, leading to a fall in oestrogen and progesterone

• as a result FSH and LH levels start to rise

What do oestrogen and progesterone do in preparation for pregnancy?

• stimulate the thickening and development of the endometrium

• When the hormone levels fall, this leads to degeneration of the endometrium and menstruation