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Phys Spring 4 Lec 4

Growth hormone Part III

Where is GH produced? By somatotropes in the anterior pituitary
What are the (4) general effects of GH? 1. Inc protein synthesis; 2. Inc fatty acid mobilization; 3. Inc bone growth; 4. Dec rate of glucose utilization
Describe the action of GH on protein metabolism Increases: transport of AAs, transcription of DNA --> RNA, translation of RNA, release of FA from adipose tissue, as nutrient supply for protein synthesis; Decreases: uptake of glucose into skeletal muscle
Describe the action of GH on lipid metabolism Increases: lipolysis and release of FA from adipose tissue, conversation of FA into acetyl-CoA; Decreases: uptake of glucose into adipose tissue
Describe the action of GH on CHO metabolism Increases gluconeogenesis by liver hepatocytes; Decreases uptake of glucose into muscle & adipose tissue
Describe the action (4) of GH on cartilage & bone 1. Inc deposition of protein by chondrocytes & osteocytes; 2. Inc rate of chondrocyte mitosis; 3. Inc conversion of chondrocytes --> osteocytes; 4. Inc activity of osteoblast --> deposit bone --> bone grows thicker!
Relate the action of GH to insulin-like GF (IGFs) GH causes liver to produce IGFs, esp IGF-1; IGF is similar to insulin
Compare & contrast GH & IGF-1 GH plasma half-life is 20-25 mins, pulsatile secretion; IGF-1 plasma hald-life is 20 hours, stabilized by binding proteins
Name the 2 actions of IGF-1 Mitogenic & anti-apoptotic: 1. Potent activator of mitosis; 2. Potent inhibitor of apoptosis
Discuss the secretion of GH Pulsatile - every 3-5hrs - interplay of somatostating & GHRH; GHRH binds to somatotropes and inc Ca transport --> Ca causes vesicle exocytosis
Stimulants for GH secretion deep sleep, exercise, hypoglycemia, excitement, stress, trauma, ghrelin, inc plasma AA levels
Inhibitors of GH secretion hyperglycemia, IGFs, somatostatin, GH itself (neg feedback)
When does the body release the most GH? Most of the daily GH release is during deep sleep.
What effect does exercise have on GH secretion? Vigorous exercise significantly inc GH secretion
What is the result of GH release due to deep sleep and vigorous exercise on glucose? Glucose is save for the brain
What is the result of GH deficiency? Extremely short stature; proportional limb growth --> GH deficiency is NOT the same as dwarfism (achondroplasia); can be treated with GH
What causes gigantism? tumor cells producing GH prior to epiphyseal plate closure
What causes acromegaly? Which areas are typically affected? GH cell tumor in adult; bones of jaw, cranium, hands, feet thicken; tongue, liver, kidney also enlarged
What happens to GH levels as you age? GH levels decline with age
What is the result of decreased levels of GH? Dec muscle (lean body) mass & inc fat mass
What are the side effects of exogenous GH? Type II diabetes, ketoacidosis, Carpel tunnel syndrome, inc rates of colon & breast cancer, edema, joint pain, gynecomastia
How does exogenous GH cause Type II diabetes? From GH-induced hyperglycemia
How does exogenous GH cause ketoacidosis? From excessive mobilization & usage of FA
How does exogenous GH cause carpel tunnel syndrome? compression d/t enlarged hand bones --> as first sx of developing acromegaly
Created by: hclark86



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