Endocrine Control of Growth and Metabolism Flashcards
What steroid hormones does the adrenal cortex release
Mineralocorticoids
Glucocorticoids
Sex Hormones
What is the primary glucocorticoid secreted by the adrenal cortex
Cortisol
What is cortisol effect in protecting against hypoglycaemia
when blood sugar decreases , glucagon, which promotes gluconeogenesis and glycogen breakdown is secreted from pancreas
Cortisol is required for full glucagon and catecholamine activity
Metabolic effects of cortisol
Promotes gluconeogenesis
Enhances lipolysis
Suppresses the immune system
causes negative calcium balance
How are thyroid hormones released from the thyroid
TRH from hypothalamus stimulates adenohypophysis to secrete TSH
TSH acts on thyroid gland to promote hormone synthesis
How does goiter occur
Elevated TSH levels lead to enlargement of the thyroid gland
What is hyperthyroidism and what are it’s effects
Excess hormone secretion
Increases oxygen consumption and metabolic heat production
Increases heart rate and force of contraction
What is hypothyroidism
What are it’s effect
Reduced hormone secretion
Decreases metabolic rate and oxygen consumption
Decreases heart rate
What word is used to describe growth hormones
Anabolic
What factors does normal growth prior to adulthood rely on
Growth hormones
Adequate diet
Absence of stress
Genetics
What stimulates GH release from hypothalamus
GHRH or somatocrinin
What does GH stimulate
Secretion of insulin like growth factors from liver and other tissues
Both GH and IGF promote protein synthesis and act on bones to increase their growth
Describe the growth hormone feedback loop
GHRH stimulates GH release from adenohypophysis
GH stimulates release of GHIH from hypothalamus and IGF form liver and other tissue
GH and IGF causes blood glucose increase and bone and tissue growth
IGF causes cartilage growth
GHIH and IGF inhibit GH release
GH and IGF inhibit GHRH release
What causes acromegaly
Oversecretion of GH and IGFs
What does soft tissue require for growth
GH, thyroid hormone and insulin
What is required for tissue protein synthesis and cell division
GH and IGFs
Where does bone growth occur in children
Epiphyseal plates
What are the steps in bone growth in children
Chondrocytes lay down new cartilage which lengthens the bone
older chondrocytes die, space left is invaded by osteoblasts which secrete calcium leading to new bone
Plates become inactive during adolescence
What are the 3 compartments that calcium is distributed in
Extracellular fluid
Intracellular Ca2+
Extracellular matrix
where and how does Ca2+ loss occur
Occurs at the kidneys
Filtered at glomerulus and reabsorbed through the proximal tubule and ascending loop of Henle
Hormonally regulated reabsorption takes place in distal nephron
What 3 hormones control ca2+ movement between bone, kidney and intestine
Parathyroid hormone
Calcitriol
Calcitonin
What is the main function of PTH and how is this achieved
Increase plasma Ca2+ concentration
Mobilizes calcium from bone
Enhances renal absorption of calcium
Increases intestinal absorption of calcium through its influence on vitamin D3
What is the function of calcitriol
Facilitates renal absorption of calcium and helps mobilise calcium out of the bone
Enhances intestinal absorption of calcium
What is does calcitonin do and when is it released
Decreases bone reabsorption and increase renal excretion of calcium
Released when plasma Ca2+ increases
