Endocrine Role in Development

Question 1

local effects/self

Answer 1

• autocrine: receptor on surface of cell secreting hormone
• intracrine: receptor inside cell secreting hormone

Question 2

distant effects

Answer 2

• paracrine: receptor on neighboring cell
• endocrine: receptor on far away cell

Question 3

morphogenesis

Answer 3

change in structure (bone growth, maturation, secondary sex characteristics)

Question 4

integration

Answer 4

regulate body process (ephinephrine/norepinephrine)

Question 5

maintenance

Answer 5

homeostasis

Question 6

changes throughout life

Answer 6

• secretion of hormones and hormone like factors changes as a function of age
• number of receptors per cell varies across tissues and changes throughout life
• receptor concentration per cell for selected hormones increases during growth and puberty and decreases during aging
• hormone concentration can also induce increases in receptors

Question 7

tropic hormones

Answer 7

regulate hormone secretion by other endocrine glands

Question 8

negative feedback loop

Answer 8

secretion regulated, presence of circulating hormones inhibits the release at both the hypothalamus and anterior pituitary, puberty switches to positive feedback

Question 9

growth hormone (GH)

Answer 9

• circulates in blood in free form or bound to a GH binding protein
• levels of binding protein are low at birth and increase rapidly throughout childhood, stable during adolescence
• influences protein, carbohydrate and fat metabolism
• decreases the rate of carbohydrate uptake and utilization by tissues
• enhances mobilization of lipids from adipose tissue deposits to meet energy needs

Question 10

IGF-1 (insulin like growth factor 1)

Answer 10

• some liver cells have receptors for GH
• stimulates protein synthesis
• increases mitosis
• has effect on cartilage and growth plates
• will drive division of chondrocytes in growth plates
• bone grows faster, but maturation isn’t accelerated
• this is happening during childhood and adolescence
• intensifies during adolescence, especially in males

Question 11

thyroid

Answer 11

• TSH from anterior pituitary stimulates production of thyroxine
• essential for normal growth and maturation because the effects of GH and IGF-1 are insignificant in the absence of thyroxine
• hypothyroidism yields growth failure including reduced rate of growth, impaired linear bone growth, infantile body proportions, delayed skeletal and sexual development
• hyperthyroidism yields excessive growth only initially
• also secretes calcitonin
• goal = lower blood calcium levels