pituitary hormones. turkish saddle intermediate lobe

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 effectsindirect effects

lipolysis in fat cells

+

carbohydratemetabolism

+

Insulin-like Growth Factor

+

muscle

chondrocytes

Protein synthesis

cartilage formation

Increases FFA, glycerol, and sugars in circulation

BrainPituitary

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 plasma2. prolong the half-life of IGF in circulation3. regulate IGF access to receptor in

extracellular fluid (!)

1. IGFBP-3most abundant form of IGFBPmain carrier of IGF in circulationpromotes IGF mediated somatic growthhigh IGFBP-3 associated growth stimulation

2. IGFBP-1typically present in small amountshigh IGFBP-1 associated growth inhibition

IGFBP-3

IGF

IGF receptor

LIVER

Cell

Growth Functions

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

BrainPituitary

Liver

IGF

IGF binding proteins (IGFBPs)

Growth

Growth Hormone (GH)

GCs

Defective GH receptor recessive gene Lethal in males

Pygmy

GAP

Hyperprolactinemia

chronic renal failure, hypothyroidism, polycystic ovary syndrome .

prolactinoma

Galactorrhea, irregular menses or infertility

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 + beta2. 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