THE ANTERIOR PITUTARY power pointxt.pptx

The anterior pituitary

1. ANTERIOR PITUTARY HORMONES DR. K.PANITHA

2. HORMONES OF ANTERIOR PITUTARY: SIX IMPORTANT HORMONES secreted from anterior pituitary: 1.Growth hormone(GH)or somatotropin. 2.Thyroid-stimulating hormone (TSH)or thyrotropin. 3.Adrenocorticotropic hormone(ACTH) or corticotropin 4.Follicle stimulating hormone(FSH)or gonadotropin 5.Luteinizing hormone(LH)or gonadotropin 6.Prolactin.

3. GROWTH HORMONE: Growth hormone is secreted from somatotrophs that constitute about 50% of the total endocrine cells of anterior pituitary. REGULATION OF GROWTH HORMONE SECRETION: Normal basal plasma GH :0ng/ml to 5ng/ml in adults. 1.GHRH stimulates & somatostatin inhibits GH secretion. 2.growth hormone in turn controls its own secretion by feedback mechanisms. Growth hormone has a negative feedback effect on GHRH.& a positive feedback effect on somatostatin secretion.

4. Growth hormone stimulates production of insulin like growth factor 1or somatomedin c, which has negative feed back effect on GH secretion. 3.insulin like growth factor 1 has effects both at pituitary and hypothalamus levels. 4.various factors regulates GH secretion by influencing secretion of GHRH ,somatostatin,IGF-1. Factors which increase: hypoglycemia, stress, puberty, stage 4 sleep. Factors which decrease: REM sleep, obesity, pregnancy.

5. GH SECRETIONS : 1.secretions occurs through out life. 2 increases during infancy & maintained through out childhood. 3.increases enormously at puberty ,which is associated with sudden increase in height & general growth of the body. 4.after puberty,GH secretion decreases . 5.growth hormone secretion is less in old age.

6. APPLIED ASPECTS: ACROMEGALY: Hypersecretion of growth hormone. Adults- acromegaly,children -gigantism. Acromegaly means enlargement of peripheral parts of the body. Features: enlargement of hands ,feet, prognathism, acromegalic facies. Glucose intolerance, hirsutism, gyneacomastia & lactation.

7. GIGANTISM: Hypersecertion of growth hormone. Features: increase epiphyseal growth of long bones. Patient is abnormally tall with gaint stature. DWARFISM: Deficiency of growth hormone. Decreased muscle and total body mass Short stature ,delayed bone and sexual maturation. Mental power is normal Low level of GH or IGF-1 in plasma.

8. FUNCTIONS: Effects on growth: stimulates linear growth ,acts on epiphysieal cartilage of long bones. Direct effect on skeletal muscle growth (protein synthesis) Effect on viscera size. Effect on metabolism: increase gluconeogenesis,decrease glucose uptake. Effect on decrease insulin sensitivity.

9. THYROID STIMULATING HORMONE: TSH is a glycoprotein. Hormone. Controls growth & function of thyroid gland. Mainly controls secretion of T3,T4.

10. REGULATION OF SECRETION: Normal plasma concentration of TSH is 0.3-5µU/ml. TRH secreted from hypothalamus,major stimulant. Somatostatin inhibits TSH secretion. Secretion of TRH is inhibited by T3 & T4 ,by negative feedback mechanism. TSH secretion exhibits diurnal variation with maximum secretion during night ,which is influenced by cortisol.

11. FUNCTIONS: Facilitates iodine uptake for thyroid gland. Stimulates release of thyroid hormones. Promotes endocytosis. Increases blood flow to thyroid gland. Causes growth and hypertrophy of thyroid gland.

12. ADRENOCORTICOTROPIC HORMONE: ACTH important hormone which controls growth & secretion of adrenal cortex. Mainly influences secretion of cortisol Plays important role in stress & stress disorder.

13. REGULATION OF SYNTHESIS:

14. FUNCTIONS: ACTH stimulates synthesis and secretion of cortisol and other steroid hormones. ACTH has intrinsic melanocyte stimulating hormone activity ,hence stimulates growth and activity of melanocytes. Acts as a local neurotransmitter. Influences immunity by control secretion of cytokines from lymphocytes.

15. LEUTINIZING HORMONE & FOLLICLE STIMULATING HORMONE: LH & FSH are called gonadotropins . Regulate growth and development of gonads ,pubertal maturation &secretion of sex steroids.

16. REGULATION OF SECRETION: secretion of gonadotropins is pulsatile,periodic,diurnal,cyclic ,& seasonal. Mainly controlled by gonadotropin releasing hormone. Gonadotropin releasing hormone secretion is influenced by various pychological , emotional and chemical factors. FEED BACK CONTROL: a. Testosterone in males and estrogen in females provide negative feedback signal to inhibit gonadotropin secretion. b. Inhibin inhibits GnRH & gonadotropin secretion. c. Activin stimulates FSH synthesis & secretion. d . Follistin inhibits FSH secretion.

17. FUNCTIONS: A.FUNCTION OF FSH: FSHstimulates granulosa cells of ovary & Sertoli cells of testis ,to secrete inhibin-B. FSH controls oogenesis & spermatogenesis. B.FUNCTION OF LH: 1. LH stimulates theca cells of ovary and Leydig cells of testis to secrete oestrogen & testosterone. 2.Sudden increase in LH concetration in middle of menstural cycle is essential for ovulation.