PBL 38 Flashcards
What is adrenarche?
The period preceding puberty
The onset of puberty is associated with which hormone increase?
GnRH
High GnRH leads to the rise in which sex hormones?
LH and FSH
Where is GnRH released from?
The hypothalamus
The cells in the … … respond to GnRH release from the hypothalamus by secreting … and …
Anterior pituitary
LH
FSH
The ovaries or testes respond to rising amounts of LH and FSH by growing and beginning to produce … and …
oestradiol and testosterone
Rising levels of which hormones produce the body changes of female and male puberty?
oestradiol
testosterone
Signs of male puberty
Voice breaks
Growth of muscle tissue
Enlargement of genitalia
Facial, pubic and axillary hair
Signs of female puberty
Broadening of hips
Menstruation begins
Development of breasts
Pubic and axillary hair
What is the name of the growth hormone?
Somatotropin
Where is somatotropin synthesised and secreted from?
Somatotrophic cells in the anterior pituitary gland
What are the direct and indirect effects of growth hormone?
Direct: result of growth hormone binding to its receptor on target cells e.g. adipocytes have growth hormone receptors which are stimulated by growth hormone to break down triglyceride and suppresses their ability to take up and accumulate circulating lipids
Indirect: mediated by IGF-1, a hormone secreted from the liver and other tissues in response to growth hormone. A majority of growth promoting effects of growth hormone is due to IGF-1 acting on its target cells
Effects of IGF-1 on growth
- Stimulates proliferation of chondrocytes (cartilage cells), resulting in bone growth
- Stimulates differentiation and proliferation of myoblasts in muscle growth
- Stimulates amino acid uptake and protein synthesis in muscle and other tissue
Production of GH is modulated by which alternate factors?
Stress Exercise Nutrition Sleep GH itself
Primary modulators of GH release
- Growth hormone releasing hormone (GHRH) - made by the hypothalamus, it stimulates synthesis and secretion of GH
- Somatostatin (SS) - produced by several types of tissues, including the hypothalamus. It inhibits GH release in response to GHRH and other stimulatory factors such as low blood glucose
- Ghrelin - peptide hormone secreted from the stomach. It binds to receptors on somatotrophs and potently stimulates GH secretion