Important Endocrine Glands and their Hormones Prof Chetana Kanekar

M.Sc Zoology ( SET life sciences)

Introduction

A hormone is a chemical substance that is secreted into the internal body fluids by one cell or group of cells and has a physiological control effect on other cells of the body.

There are different types of hormones

Local Hormones General Hormones

Local Hormones

Acetylcholine released at the parasympathetic and skeletal nerve endings.

Secretin released by the deudenal wall and transported in the blood to the pancreas to cause a watery pancreatic secretion.

Cholecystokinin released in small intestine and transported to the gall bladder to cause it to contract and to the pancreas to cause digestive enzyme secretion.

These hormones have specific local effects, from where it comes the name local hormones.

General Hormones

General hormones are secreted by specific endocrine glands.

Important hormones secreted by these glands and their most important actions

Anterior Pituitary Gland

1. Growth Hormones

2. Adrenocorticotropin

3. Thyroid Stimulating Hormones(TSH)

4. Follicle Stimulating hormones(FSH)

5. Leuteinizing hormones(LH)

6. Prolactin

Posterior Pituitary gland

1. Antidiuretic hormone

2. Oxytocin

I. Pituitary Gland hormones

1. Growth hormone causes growth of almost all cells and tissues of the body.

2. Adrenocorticotropin causes the adrenal cortex to secrete adrenocortical hormones.

3. TSH causes the thyroid gland to secrete thyroxine.

4. FSH causes the growth of follicles in ovaries before ovulation, promotes the formation of sperm in the testis.

5. Prolactin promotes development of breasts and secretion of milk

Functions of hormones secreted from

Pituitary gland.

Antidiuretic hormone also called as vasopressin causes the kidneys to retain water ,thus increasing the water content of the body ,also in high concentration causes constriction of blood vessels throughout the body and elevates the blood pressure.

Oxytocin hormone contracts the uterus during the birthing process , thus helping expel the baby, also contracts myoepethelial cells in the breasts,thereby expressing milk from breast when baby suckles.

II. Adrenal cortex hormones

1. Cortisol:- Cortisol for control of the metabolism of proteins, carbohydrates and fats.

2. Aldosterone :- Aldosterone reduces sodium excretion by kidneys and increases potassium excretion, thus increasing sodium in the body while decreasing the amount of potassium.

III. Thyroid Gland 1. Thyroxine 2. Triidothyronine :- Function of 1 & 2 increase the rates

of chemical reaction in almost all cells of the body, thus increasing the general level of body metabolism.

3. Calcitonin:- It promotes the deposition of calcium in the bones and thereby decreases calcium concentration in the extra cellular fluid.

IV. Islets of Langerhans in the Pancreas

1. Insulin :- It promotes glucose entry into most cells of body , in this way controlling the rate of metabolism of most carbohydrates.

2. Glucagon :- It increases the synthesis and release of the glucose from the liver into circulating body fluids.

V. Ovaries

1. Estrogen :- It stimulates the development of the female sex organs ,the breasts and various secondary sexual characteristics.

2. Progesterone :- It stimulates secretion of uterine milk by uterine endomentrial glands; also helps promote development of secretory apparatus of the breasts.

VI. Testis

Testosterone:- It stimulates growth of the male sex organs, also promotes the development of male secondary sex characteristics.

VII. Parathyroid Gland

Parahormone :- It controls the calcium ion concentration in the extracellular fluid by controlling absorption from the gut , excretion of calcium by the kidneys and release of calcium from the bones.

VIII. Placenta

1. Human Gonadotropin:- It promotes growth of the corpus luteum and secretion of estrogens and progesterone

2. Estrogens:- It promotes growth of the mother’s sex organs and some of the tissues of the foetus.

3. Progesterone:- It promotes development of endometrium in advance of implantation of the fertilized ovum ; probably promotes development of some of the fetal tissues and organs; helps promote development of the secretory apparatus of the mother’s breasts.

4. Human somatomammotropin:- It probably promotes growth of some fetal tissues as well as aiding in development of the mother’s breasts.

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