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Phys Spring 4 Lec 4
Growth hormone Part III
| Question | Answer |
|---|---|
| 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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