Download Peptide Hormones

Dr. Areej M. Al-Taweel
Pharmacognosy Department
Chemical Classification of Hormones
A- Steroidal Hormones:
1- Adrenocorticoids:
Glucocorticoids
Mineralocorticoids
e.g. Hydrocortisone.
e.g. Aldosterone.
2- Sex Hormones:
Female sex hormones
Male sex hormones
e.g. Estrogens and Progestins
e.g. Androgens.
B- Amino acids derived hormones:
1- Hormones derived from single amino acid e.g. Thyroxin.
2- Peptide hormones:
i- Only amino acids:
*Anterior Pituitary hormones:
- Prolactin
- Growth Hormone
- Placental lactogen.
* Corticotropins: Adrenocorticotropic hormone ACTH.
* Insulin
* Parathyroid hormone and Calcitonin.
ii- Glycoproteins (Amino acids and sugars):
*Anterior Pituitary Hormones:
- Leuteinizing hormone (LH)
-Follicle Stimulating hormone (FSH)
- Chorionic Gonadotropin (CG) -Thyroid Stimulating hormone (TSH).
Mechanisms of
Hormonal Actions
I- Peptide Hormones
 Peptide hormones do not enter the cell
but bind to plasma membrane receptors.
■
■
Peptide hormones combine with
membrane receptors that activate
signal transduction.
Many hormones use a G protein-linkedadenylyl cyclase-cAMP second messenger.
 Second messengers activate other
intracellular chemicals to produce
the target cell response.
II-Steroid Hormones
■
Once inside the cell the steroid hormone binds with a specific
receptor found only in the cytoplasm of the target cell.
The receptor bound steroid hormone then travels into the nucleus.
 The activated hormone-receptor complex binds to DNA and
initiates transcription of a particular gene. The result is production
of messenger RNA followed by protein synthesis.
(new protein produce change in cellular activity)
Thyroid Hormones

Thyroid Gland:
Highly vascular flat structure.
 Located at the upper portion of the trachea.
 Composed of twp lobes.

Hormones of the Thyroid gland:

Thyroid gland secretes Thyroxin T4 and lesser amounts of
triiodothyronine (T3).

Calcitonin.
Thyroxin and Tiiodothyronin
* Structures: Derived from single amino acid.
I
HO
I
NH2
CH2CH COOH
O
I
I
Thyroxine
I
5'
HO
NH2
CH2CH COOH
O
I
I
Triiodothyronine
Structure Activity Relationship

Angle between the two aromatic rings must be 1200.

3’-Monosubstituted molecules are more active than 3’, 5’disubstituted ones.

Triiodothyronin is 4 times more active than Thyroxin.

3’-Isopropyl derivative is 7 times more active than
Thyroxin.

Regulation:
Hypothalamus
Thyrotropine Releasing Hormone
(TRH)
Anterior Pituitary
Thyroid Stimulating Hormone
(TSH)
Thyroid gland
Thyroxin & Triiodothyronin
Stimulation: TRH
Inhibition:
-ve Feed-back mechanism.
When blood concentrations of thyroid hormones increase
above a certain threshold, TRH-secreting neurons in the
hypothalamus are inhibited and stop secreting TRH.
Actions of the Thyroid Hormones:





Enhance growth and protein synthesis.
Essential for the development of the nervous system.
Increase oxygen consumption and basal metabolic rate.
Increase body temperature.
Cardiovascular effect:
 Increase
heart rate.
 Increase force of contraction.
 Increase cardiac output.
Disorders of thyroid function include:
* Hypothyrodisim
- In infants, cretinism
- In adults this cause myxoedema
* Hyperthyrodisim either:
- Diffuse toxic goiter
- Toxic nodular goiter
Disorders of thyroid function
Hypothyroidism in children (Cretinism)
Cretinism:

Irreversible condition due to deficiency of thyroxin
soon after birth.

Retardation in physical and mental development.
Sign and symptoms of Cretinism:
- Mental retardation
- Large head
- Swollen eye lids
- Flattened nose
- Temperature below normal
- Enlarged tongue
- Grows very slowly.
- Poor metabolism
- Thick, dry, cool skin
Disorders of thyroid function
Hypothyroidism (Adult)
Myxoedema:
 Deficiency
of thyroxin in adults due to:
Removal of thyroid gland by surgery.
 Destruction of the gland by Radioactive Iodine.
 Atrophy of the thyroid gland.

Symptoms of Myxedema:
 Muscle
weakness.
 Slow heart rate and low cardiac output.
 Dry cold and thick skin.
 Brittle coarse hair.
 Puffy expressionless face.
 Decreased sweating
 Increase body weight and body fat
Treatment:
 Thyroxin for life.
eg. :L-Thyroxin sodium
(Synthyroid)