HORMONES (1)
HORMONES
• Chemical messengers of the body.
• They are transported to tissues or organs via blood circulation
• They work slowly but affect many metabolic functions.
Endocrine Effect: Affect a tissue far away from where the hormone is secreted
Paracrine Effect: Affect the adjacent cell
Autocrine Effect: It is the same hormone affects the cell that it is secreted.
In addition to endocrine effects, some hormones have autocrine and paracrine effects.
Endocrine Glands
- Hypothalamus - Pituitary
- Thyroid - Parathyroid - Ovary
- Testis
- Adrenal Glands - Pancreas
HYPOTHALAMUS
GnR
H CRH TR
H
PR
H GHR
H Pituitary
FSH/L
H Prolact
TSH in ACT
H
Target Cell
ADH Oxytoci n
GH
Anterior lob Posterior lob
ADH Oxytoci n
1. Oxytocin
- Stimulation of the contraction of smooth muscles during childbirth and lactation
- Oxytocin is often given to speed up childbirth
- It is important for milk to be released after childbirth.
Hypothalamic Neuropeptides
.
2. ADH (Antidiüretic Hormone- Vasopressin)
- Effects kidney tubule cells
- Provides the retention of filtered water from the kidneys
- Concentrates the urine
- Increases the permeability of the tubules to water - Causes blood vessels to contract
- The most important factor controlling the vasopressin secretion is the osmolality of the blood.
↓
↓
↓
Plasma osmolality↑
Pituitary
ADH
Water permeability of kidney collection channels ↑
↓
Plasma osmolality ↓
Diabetes İnsipidus
• The pituitary gland produces insufficient ADH
• Urine amount increases
2. ADH (Antidiuretic hormone-
Vasopressin)
Anterior pituitary Hormones
1. TSH (Thyroid-stimulating hormone) 2. Gonadotropins (LH and FSH)
3. Somatotropin (GH) 4. Prolactin
5. Adrenocorticotropic hormone (ACTH)
Anterior pituitary Hormones 1
.TSH (Thyroid-stimulating hormone)
Hypothalamus TRH
↓
Pituitary TSH
↓
Thyroid Gland
-
- -
Thyroid hormones
Negatif feed back
2. Gonadotropines (LH and FSH):
- Primary effects in women; egg
development, implantation and normal growth of the fetus
- FSH;
- Stimulates the development of follicles in the ovaries and sperm in the testicles - LH ;
- It is effective on the production of steroid hormones.
- Stimulates Leyding cells to produce testesterone and stimulates corpus
luteum to produce progesterone in the ovaries.
- The main stimulus for LH and FSH comes from GnRH
.
. H
Hypothalamus GnRH
Pituitary FSH, LH
Testis and ovary
↓
Testester one
Estrogen and
progester one
-
-
+↓ ↓
-
-
3. Somatotropin (GH):
.
The main effect is to stimulate the growth of the organism
Stimulates the growth of long bone and soft tissue.
GH affects carbohydrate, protein and fat metabolism.
Reduces glucose uptake by muscle cells and adipose tissue
Liver …..Gluconeogensis ↑, glycogenolysis ↑ blood glucose levels ↑
Shift from glucose to lipids as an energy source
Increases amino acid uptake of cells.
It has anabolic effects on protein metabolism.
Increases lipolysis in fat cells, increases the use of oils for energy
GH secretion increases with GHRH.
Somatostatin is secreted from the hypothalamus.
Inhibits GH secretion from adenohypophysis
3. Somatotropin
(GH):
3. Somatotropin (GH):
It modulates the activities of liver, kidneys, bone, cartilage, skeletal muscle and fat cells.
3. Somatotropin (GH):
GH deficiency before puberty …… . short stature Over secretion before puberty ……. Gigantism
After adolescence, GH excess …… thickening of long bones, facial contours become rough, feet and hands grow.
4. Prolactin
- It is controlled by the PRH released from the hypothalamus.
- Its level in the blood increases during pregnancy.
- It causes the development of mammary glands in females.
- It increases the synthesis of milk proteins and milk production.
- It prepares the mammary glands for lactation during pregnancy, but there is no milk secretion. It provides lactation to start and continuity after birth.
5. Adrenocorticotropic hormon (ACTH):
Hypothalamus CRH
Pituitary ACTH
Adrenal glands
Cortisol
-
↓ -
↓
5. Adrenocorticotropic hormon (ACTH):
Cushing syndrome:
- Excessive production of ACTH is seen.
- Abnormal cortisol release
- Cortisol secreting tumor of the adrenal cortex
- Mobilization of fats from the underside of the body, - Excessive storage of the chest and upper abdomen - Edema in the face
- Purplish lines in subcutaneous tissues
Physicochemical Properties of Hormones
• Hydrophobic: Steroidal hormones
• Hydrophilic: Peptide hormones and Thyroid Hormones
Mechanism of action of hormones
• Hormones must bind with their original receptors to show their effects when they reach the target tissue / cells.
• Receptors are located in the cell membrane, cytoplasm or nucleus.
HORMONES;
Hormone receptors are on the surface of the cell or inside the cell
Regulation of Hormone
Secretion
Mechanism of Hormone Action- Receptor-Signal Transduction
• Steroidal structure hormones
• Aminoacid structure hormones
• Peptid (polypeptide) structure hormones
Cell
Membrane
Glucorticoids enter the cell and activate cytoplamic or nuclear receptors.
Activated receptors initiate the
transcription of genes sensitive to glucocorticoids.
The DNA binding region of the activated receptor has increased interest to the
specific glucocorticoid response elements.
Action Mechanism of Steroid and Thyroid hormones
• Location of receptor: Cytoplasm/Nucleus
• Hormone-Receptor Interaction?
Mechanism of Hormone Action in polypeptide structure
• Second Messengers: DAG, Ca+2 , IP3, cAMP, cGMP
• Effector Molecule Adenilate cyclase, guanilate cyclase
• Protein kinases: PKA, PKC
• Locaction of Receptors: Cell Membrane
• 1. Channel-type receptors : Calcium channels
2. G-protein bound receptors : Glukagon, alfa –adrenerjik receptors
• 3. Enzyme-type receptors (Tyrosine Kinase ): Insulin Receptors
REFERENCES
• The Endocrine System An Overview Susanne Hiller-Sturmhöfel, Ph.D., and Andrzej Bartke, Ph.D, Vol. 22, No. 3, Alcohol Health & Research World1998
• MONTGOMERY - CONWAY-SPECTOR-CHAPPEL, BİYOKİMYA OLGU SUNUMLU YAKLAŞIM, Çeviren: Nilgün Altan
• Lippincott’s Illustrated Reviews Series Editor: Richard A. Harvey Biochemistry Denise R.
Ferrier
