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