Growth and Development • Two hypothalamic hormones control growth hormone synthesis and secretion in the anterior pituitary gland ➢ Growth hormone–releasing hormone (GHRH)stimulatesthe pituitary to release growth hormone ➢ Somatostatin inhibitsthe secretion of both GHRH and thyroid-stimulating hormone • Brain: peak fetus, early infancy • Skeleton: peak fetus, infancy, adolescence • Muscle: peak fetus, adolescence • Adipose: peak infancy, adolescence • Lymphoid: peak age 10 to 12 years • Neural: peak age 4 to 14 years • Genital: peak adolescence • Fetus ➢ Head growth predominates • Infant ➢ Trunk growth predominates ➢ Weight gain at rapid but decelerating rate • Child ➢ Legs are fastest growing ➢ Weight gained atsteady rate • Adolescence ➢ Trunk and legs elongate. ➢ 50% of ideal weight is gained. ➢ Of adults who are obese ➢ 30?come obese during childhood ➢ 70?come obese during adolescence ➢ Skeletal mass and organ systems double in size. • Pregnant Women ➢ Progressive weight gain, fetus 6-8lbs is expected, rest of weigh is from maternal tissue and fluids, weight gain isslow in 1st trimester, rapid in 2nd and slowsin the 3rd • Older adult ➢ Stature declines beginning at 50 (thinning of discs, kyphosis) ➢ Increase in overweight and obese older adults ➢ Decrease in weight for height and BMI among those over 60 ➢ A loss of 5% of body weight over several years occurs accompanied with an increase in body fat as skeletal muscle declines (due to decreased exercise and reduced anabolic steroid secretion) ➢ Reduction in the size and weight of organs (liver, lungs, kidneys)