Pituitary Hormones
Turkish saddle
Intermediate Lobe
(I) somatotropes that secrete GH (2) mammotropes that secrete PRL (3) thyrotrophs that secrete TSH (4)gonadotropes, single cells that secrete both gonadotropins LH and FSH (5) corticotropes that secrete both ACTH and ß-LPH
1- Growth Hormone Family (GH, PRL, CS) 2- Glycoprotein Family(TSH,LH,FSH,HCG) 3- POMC Family (ACTH,ß-LPH, Endorphins)
GH Receptor and jak2 From: Herrington & Carter-Su (2001)
GH signalling From: Herrington & Carter-Su (2001)
GHIH (or) SST (somatostatin) (-) Anterior Pituitary: Hypothalamus: GHRH (+) GH (somatotropin) Liver: IGF (somatomedins) (+) (-)
GROWTH HORMONE direct effects indirect effects lipolysis in fat cells + carbohydrate metabolism + Insulin-like Growth Factor + muscle chondrocytes Protein synthesis cartilage formation Increases FFA, glycerol, and sugars in circulation
Brain Pituitary Liver IGF IGF binding proteins (IGFBPs) Growth Growth Hormone (GH)
IGFBPs bind circulating IGF with high affinity & specificity Functions: 1. act as carriers of IGF in plasma 2. prolong the half-life of IGF in circulation 3. regulate IGF access to receptor in extracellular fluid (!)
1. IGFBP-3 most abundant form of IGFBP main carrier of IGF in circulation promotes IGF mediated somatic growth high IGFBP-3 associated growth stimulation 2. IGFBP-1 typically present in small amounts high IGFBP-1 associated growth inhibition
IGFBP-3 IGF IGF receptor LIVER Cell Growth Functions
Cell IGF receptor LIVER IGFBP-1 IGF
Growth Hormone Direct effects: Lipolysis Carbohydrate metabolism Increase IGF secretion from liver Indirect effects through IGF Increase protein synthesis in muscle Increase cartilage formation and growth in bone IGFBPs IGFBP3 enhances growth IGFBP1 inhibits growth
Overproduction of GH Underproduction of GH End-organ resistance
Overproduction of GH Acromegaly gigantism Underproduction of GH panhypopituitarism Stress-induced dwarfism End-organ resistance
Brain Pituitary Liver IGF IGF binding proteins (IGFBPs) Growth Growth Hormone (GH) GCs
Defective GH receptor recessive gene Lethal in males Pygmy
GAP
Hyperprolactinemia chronic renal failurechronic renal failure, hypothyroidism, polycystic ovary syndrome.hypothyroidismpolycystic ovary syndrome prolactinoma Galactorrhea, irregular menses or infertilitymensesinfertility headaches
1. TSH – to stimulate the secretion of thyroid hormone 2. FSH & LH – important for the function of the testes and the ovaries FSH – growth of ovarian follicles and formation of sperm LH (in women) – induce ovulation and the formation of the corpus luteum; stimulate the ovarian production of estrogen and progesterone LH (in men) – stimulates the production of Testosterone;
1. 2 peptide subunits– alpha + beta 2. The three glycoprotein hormones and hCG (Human chorionic gonadotropin; a placental hormone) all share the same alpha subunit. 3. Both subunits need to be present to be functional. 4. Beta subunits are encoded in separate genes located on different chromosomes.
4 Glycoproteins– all of them share a common alpha subunit
Pro-opiomelanocortin (POMC), a gene, products Melanocyte-stimulating hormone (MSH) Corticotropin-like intermediate lobe peptide (CLIP) P. convertases