Endocrine System

Some specific Endocrine Glands and their Hormones


 Adrenal Gland

The ductless gland found on kidney is called as adrenal gland. Each kidney has an adrenal gland on it. This gland is also called as “Supra Renal Gland”. It has two parts- the upper- cortex and the lower- medulla.

The hormone secreted in this gland increases blood pressure after getting mixed into it. Adrenalin is the principal hormone secreted by this gland. This hormone works directly on heart.

Following are the hormones secreted by the adrenal cortex-

(i). Androgenic Hormone – This hormone controls sexual behaviour

(ii). Aldosteron – This hormone controls Reabsorption of salts I the Nephrons and establishes water balance in the body.

(iii). Hydrocortisone – This hormone controls the secretion of gastric juice in the stomach. Besides this, hydrocortisone controls the metabolism of carbohydrate, fat and protein.

Following are the hormones secreted in the Adrenal Medulla-

(i) Epinephrine or Adrenalin- It is a heart stimulating hormone. It causes increase in the blood pressure. When the heart stops beating due to some reason doctors may use it as medicine to restart its functioning. It is helpful in the carbohydrate metabolism also.

(ii) Non-epinephrine – It contracts blood vessels and causes increase in the blood pressure.

Thymus Gland

This is a lymphoid organ located behind sternum and between lungs of vertebrates. It produces a hormone Thymosin which stimulates the development of disease fighting c-cells- T-lymphocytes for the immune system. It remains active until puberty. After puberty, this gland starts shrinking slowly and becomes replaced by fat.

Pineal Gland

It is a small ductless gland which is found near the corpus callosum of the brain. It secretes a hormone which is concerned with the activities of sex organs. Lots of researches are needed on this gland. Through researches on this gland in rat, it has been proved that this gland secretes melatonin which affects skin colour.

Islets of Langerhans

Irregularly shaped patches of endocrine tissue located within the pancreas of most vertebrates including man, are called as Islets of Langerhans. They are named for the German physician Paul Langerhans who first described them in 1869. About 1,000,000 islets are found in a normal human pancreas.

Hormones secreted by Islets of Langerhans

Islets of Langerhans (pronounced as eye-lets) make the hormones Insulin and Glucagon. In fact, Islets of Langerhans contain two types of cells – Alpha cells and Beta cells. Alpha cells make Glucagon whereas Beta cells make Insulin.

Beta cells sense sugar in the blood and release the necessary amount of Insulin to maintain the normal blood sugar level. When the immune system mistakenly sees beta cells as “Potential Danger” and destroys them. Thus, the production of insulin decreases and a disease called Diabetes is caused.

Basically, hormone Insulin is a protein which contains an alpha chain of 21 amino acids linked by two di-sulphides (S-S) bridges to a Beta chain of 30 amino acids. Beta cells can sense glucose level of glucose in blood through their plasma membrane. These cells secrete insulin in response to rising levels of glucose circulating in blood.

Insulin hormone was discovered in 1921 by Banting. It is a complex protein which has following functions-

(a).Metabolism of Glucose – converts extra-glucose into glycogen to store inside liver cells,

(b).It is helpful in the storage of proteins in tissues so that the stored protein can be utilised during emergencies, and

(c).It induces growth in animals.

Diabetes is a disease caused due to irregular sugar levels in the blood. This condition leads to many harmful effects. The treatment of diabetes is done through injecting insulin in the patient’s body just at the time of taking food


Testes and Ovary are male and female reproductive parts respectively. These are also collectively called as Gonads. Testes produce male reproductive units or sperms whereas ovary produces female reproductive units called as ova. Besides producing sex- units these glands also function like ductless glands or endocrine glands and produce hormones. The details are as below –

(A). Testes: It secretes a group of hormones named Androgens that include Testosterone which is the principal male hormone of this group. It is mainly secreted in mails and in least volume in females. Its functions are listed below-

        (i) Development of secondary sexual characters- the secondary sexual characters are features that appear at sexual maturity in animals and humans. In humans the heaviness of voice, development of hair on face and around sex- organs, development of mammary glands in females, development of internal parts of reproductive system in females etc. are called secondary sexual characters.

        (ii) It coordinates with the hormones secreted in anterior part of pituitary and helps in the growth of tissues. It reduces the process of growth of bones.

(b) Ovary: Names and functions of hormones made by ovary are mentioned below-

Estrogen: Group of steroids or female sex hormones which promote the development and maintenance of female characteristics of the body are called as estrogen. Steroid is an organic compound which includes dietary lipid cholesterol, sex hormone testosterone, estradiol and dexamethasone. Estrogens are produced in the follicles of ovary and released in synchronization with each monthly menstrual cycle.


(i).These hormones play essential roles in the growth and development of female secondary sexual characters such as development of breasts, development of pubic hair and armpit hair, development of endometrium, and the reproductive system.

(ii). Estrogen acts to produce an environment suitable for fertilization, implantation and the nutrition of the early embryo.

(iii). It is helpful in the regulation of menstrual cycle.

(iv). It stimulates production of progesterone from placenta.


It is a female hormone secreted by corpus leutium of the ovary. It is produced just after the process of fertilization. It is helpful in the formation of internal wall or endometrium of the uterus. Most of the changes that occur in a female after pregnancy are produced due to the activity of this hormone. Some changes that occur due to the secretion of progesterone are – attachment of embryo with the wall of uterus, structure of placenta, development of milk secreting villi in mammary glands etc.


This hormone is secreted in the last stage of pregnancy. It checks the contraction of uterus and broadens vulva. Thus it helps in coming out of embryo. It also helps regulate the secretion og blood in the mammary gland.

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