Human Endocrine System

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Human Endocrine System :: Human Endocrine System Gonads

Formed by endocrine glands ( or Ductless Glands ) and their secretion. They secrete hormones directly into the blood stream in response to instructions from the brain. The blood then carries them around the body.

Endocrine Glands


Forms a part of fore – brain, secretes neurohormones, which effect the release of hormones from pituitary. Acts as the thermostat. Pituitary Gland

Also called Master Gland. It is the smallest endocrine gland. It secretes :

1. Somatotrophic Hormone ( Growth stimulating Hormone ) : Controls the general growth of the body.

Its hypersecretion leads to acromegaly in adults and gigantism in children. Its hyposecretion leads to dwarfness in children.

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2. Gonadotrophic Hormone ( GTH ) : Stimulates the primary sex hormones, i.e. ovaries and testes.

GTH are Follicle stimulating Hormone ( FSH ) and Luteinizing hormone (LH).

  • Follicle Stimulating Hormone ( FSH ) : It is secreted in males and females both. In males, it stimulates spermatogenesis and development of seminiferous tubules. In females, it stimulates formation and growth of ovarian follicle in ovary.
  • Luteinizing Hormone ( LH ) : In females only. Final maturation of ovarian follicleand ovulation takes place by LH only.

3. Lactogenic Hormone : Initiates milk production in the pregnant females.

4. Thyrotrophic Hormone : Aids in the regulation of thyroid secretion.

5. Adrenocorticotrophic Hormone ( ACTH ) : Influences the secretion from the cortex of adrenal glands.

6. Diabetogenic or Metabolic Hormone : Influences metabolism of carbohydrates, fats and proteins.

7. Oxytocin or Pitocin : Stimulates smooth muscle contractions, especially of the uterus during child birth. Also helps in the secretion of milk in females.

8. Vasopressin or ADH ( Anti – Diuretic Hormone ) : Regulates reabsorption of water from the kidney tubules.

Its Hypoactivity leads to Diabetes insipidus in which patients excrete large amount of urine.

Also causes contraction of small arteries, causing increase in Blood Pressure.

Thyroid Gland

It is the largest endocrine gland located in the neck between the trachea and larynx.

Controls BMR ( Basal Metabolic Rate ). BMR is die minimum energy requirement for maintenance of body during rest or sleep.

For normal human adult, it is 1600 Kcal / day.

Thyroid Gland Secretes :

1. Thyroxine : Regulates physical, mental and sexual development.
Hypoactivity in children leads to cretinism. Hypoactivity in adults leads to Myxoedema ( sluggish appearance, feeble mindedness, low body temperature ).

A diet, poor in iodine, which is insufficient for the synthesis of thyroxin, leads to simple goitre.

Its hyperactivity leads to increased metabolic activities (highly nervous, overactive and irritated person). Sometimes it leads to Exophthalmic goitre ( Grave’s disease ) (bulging eyeballs, irregular heartbeat, loss of weight).

2. Thyrocalcitonin : It controls the amount of calcium in the body.

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Note :

Hashimoto Disease : Due to age factor or injury in thyroid gland secretion of thyroid reduces.

When thyroxine secretion falls up to minimum limit, antibodies formation starts against the gland.

So thyroid gland is destroyed. It is known as suicide of the thyroid.

Parathyroid Gland

Secretes Parathormone, which is also known by the name of Collip’s Hormone.

It influences calcium and phosphorus metabolism ( Ca level = 12 mg / 100 ml of blood )

Removal of this gland leads to death due to tetany ( cramps, tremors and convulsions in muscles )

Hyperactivity withdraws calcium from bones leading to weakness and pain.

Thymus Gland

  • Situated near the heart.
  • Produces Thymine.
  • Plays important role in formation of antibodies in children.
  • Decreases in size as sexual maturity increases as it absorbs GTH, thus preventing development of gonads.


It is an exocrine as well as an endocrine gland. Its endocrine part is known as Islets of Langerhans. Its 3 types of cells secrete 3 different hormones.

Beta cells secrete Insulin which controls the amount of sugar in the blood. Its hyposecretion leads to Diabetes Mellitus. Alpha cells secretes Glucagon which increases blood sugar level.

Gamma cells secrete Somatostatin which controls the functioning of alpha and beta cells.

Adrenal Glands

2, on each kidney. Adrenal gland is also known as 4S gland. ( 4S stands for: Sugar metabolism, Salt retention, Sex hormone and Source of energy ).

Consists of 2 Distinct Parts : Outer cortex and inner medulla.

1. Adrenal Medulla secretes Adrenaline or epinephrine which effects liberation of glucose from glycogen stored in liver and increases the rate of metabolism.

  • Its over – secretion leads to increased saliva flow, tears, bile and sweat, quickens heart beat, speeds up respiratory activities. It is also known as 3F Gland because of these ( fear, fight, flight ).
  • Nor – epinephrine or Nor – adrenaline is also secreted from medulla (20%) which is opposite to adrenaline.

2. Adrenal Cortex secretes two types of Hormones :

  • Mineralo Corticoids : Maintain electrolyte balance in the body and distribution of water to the tissues. It. is also known as salt retaining hormone. Its hyposecretion results in Addison’s disease. In this disease, excessive loss of Na, Cl ions takes place and level of K ions increases in blood. Its hypersecretion leads to retension of Na, Cl ions and more absorption of water.
  • Gluco Corticoids : It influences carbohydrate metabolism and also effect protein and fat metabolism. Its hyposecretion leads to fall in glucose level due to which body temperature decreases. Its hypersecretion leads to Cushing Disease in which irregular deposition of fat takes place and glucose level increases in blood.

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