Diversity of Endocrine system

By

Dr. Kamal Modi

3rd year Resident

Biochemistry dept.

Communication system

Nervous system ---> fixed

Endocrine system ----> mobile

Target cell

Any cell in which the hormone (ligand) binds to its receptor, whether or not a biochemical or physiologic response has yet been determined.

How Target cell discriminate between Hormone and other similar molecules ????

Ans: Receptors

All receptors have at least two functional domains.

1) A recognition domain binds the hormone ligand

2) second region generates a signal that couples hormone recognition to some

intracellular function.

Group 1

Hormones that bind to intracellular receptors

Lipophilic

Require transport proteins

E.g. Steroids, Iodothyronines Retinoids

Group 2

Bind to cell surface receptors

Hydrophilic E.g Catecholamines

LH, FSH, HCGInsulin, Glucagon

Mediates through cAMP, cGMP,Ca, Kinase Cascade

Hormone synthesized in Various cellular arrangements.

In discrete organ designed solely for this purpose.

Thyroid Adrenal Pituitary

T3, T4 Gluco-corticoidsMineralo-corticoids LH

FSHTSHGH

In specialized cells within other organs.

Small intestineThyroid Kidney

Glucagon Calcitonin Angiotensin II

Requires the parenchymal cells of more than one organ.

Skin Liver Kidney

Calcitriol

Hormones are Chemically diverse

synthesized from a wide variety of chemical building blocks.

hormone is the precursor molecule for another hormone.

Amino acid tyrosine is the starting point in the synthesis of the catecholamines and of the thyroid hormones tetraiodothyronine (thyroxine; T4) and triiodothyronine (T3).

T3 and T4 are unique in that they require the addition of iodine for bioactivity.

Many hormones are polypeptides or glycoproteins.

Hormones Are Synthesized & ModifiedFor Full Activity in a Variety of Ways

synthesized in final form and secreted immediately. E.g. hormones derived from

cholesterol.

synthesized in final form and stored inthe producing cells. E.g. Catecholamines

synthesized from precursor molecules in the producing cell, then are processed and

secreted. E.g. Insulin

Converted to active forms from precursor molecules in the periphery (T3 and DHT).

Thank you...