In kidney, endocrine gland secretes the hormones such as Renin, Erythropoietin and calcitriol.
(i) Renin secreted by Juxta glomerular cells [JGA], which increases blood pressure when angiotensin is formed in blood.
(ii) Erythropoietin is also secreted by the JGA cells of the kidney and stimulates erythropoiesis in bone marrow
(iii) Calcitriol is secreted by proximal tubules of nephron. It is an active form of vitamin 'D₃' which promotes calcium and phosphorus absorption from intestine and accelerates bone formation.

(i) The hormones are chemical messengers released into the blood and circulated as chemical signals.
(ii) They influence the metabolic activities of the body by means of hormones.
(iii) Deficiency or excess secretion of hormones will lead to disorders.
(iv) Thus hormones act as chemical messenger and coordinate different physical, physiological mental activities and maintain homeostasis.

1. The butterfly shaped thyroid gland is a bilobed gland located below the larynx on each side of upper trachea. It is the largest endocrine gland in the body.
2. Its two lateral lobes are connected by a median tissue mass called isthmus.
3. Each lobe is made up of many lobules. The lobules consist of follicles called acini (acinus In singular).
4. Each acinus is lined with glandular, cuboidal or squamous epithelial cells which is filled with thick glycoprotein mixture consist of thyroglobulin molecules.
5. This acini of thyroid gland are often called as major metabolic hormones.
6. The follicular cells of thyroid gland secretes two hormones they are tri-iodothyronine (T₃) and thyroxine [tetra-iodothyronine] (T₄).
7. The parafollicular cells or 'C' of thyroid gland secretes a hormone called thyrocalcitonin.
8. To produce thyroid hormones Iodine is very essential.

1. A group of specialized endocrine cells present in gastro intestinal tract secretes hormones such as gastrin, cholecystokinin, secretin and gastric inhibitory peptides.
2. Gastrin acts on the gastric glands and stimulates the secrete of HCI and pepsinogen.
3. Cholecystokinin [CCK] is secreted by duodenum in response to the presence of fat and acid in the diet.
4. Secretin acts on acini cells of pancreas to secrete bicarbonate ions and water to neutralize the acidity.
5. Gastric inhibitory peptide [GIP] inhibits gastric secretion and motility.

(i) Pancreas is a dual hormone which performs both the function of exocrine and endocrine glands.
(ii) It is a leaf like structure composed of two major tissues such as acini and islets of Langerhans.
(iii) Insulin is a peptide hormone and play an important role in glucose homeostasis.
(iv) When entire pancreas is removed, the body is left without the cells that produce insulin and hormones that help maintain safe blood sugar level. This leads to diabetes.

(i) Adrenalin hormones secreted by adrenal medulla
(ii) Adrenal medulla secretes the hormones adrenalin and noradrenalin and are referred as 3F Hormones ie [fight, flight and fright hormones]
(iii) During emergency it increases heartbeat rate and blood pressure.
(iv) Adrenalin increases liver glycogen breakdown into glucose and increases the release of fatty acids from fat cells.
(v) It stimulates the smooth muscles of cutaneous and visceral arteries to decrease blood flow.
(vi) It increase blood flow to the skeletal muscles thereby increases the metabolic rate of skeletal muscles, cardiac muscles and nervous tissue.

(i) In human, the pineal gland is situated behind the third ventricle of brain.
(ii) It is otherwise known as cerebri or conarium and formed of parenchymal cells and interstitial cells.
(iii) It secretes the hormone, melatonin, which plays a central role in the regulation of circadian rhythm of our body and maintains the normal sleep wake cycle.
(iv) It also regulates the timing of sexual maturation of gonads.
(v) In addition to this it play a important role in metabolism, pigmentation, menstrual cycle and defense mechanism of our body.

Somatotropic hormone is important for normal growth because it performs several duties like.
(i) It promotes growth of all the tissues and metabolic process of the body.
(ii) It promotes the metabolism of Carbohydrates, proteins and lipids and increases the rate of protein biosynthesis in the cells.
(iii) It increases the release of fatty acids from adipose tissue and decreases the rate of glucose utilization for energy by the cells. It helps to minerals retention in the body like nitrogen, potassium, phosphorous and sodium.
(iv) The hyper secretion and hypo secretion of growth hormones leads to several disorders like dwarfism, gigantism and acromegaly.

Cretinism is due lower secretion of growth hormone in infants; [ie] hypothyroidism.
Symptoms of Cretinism:
In infants, hypothyroidism causes cretinism .A cretin shows
1. Retarded skeletal growth
2. Absence of sexual maturity.
3. Retarded mental ability.
4. Thick wrinkled skin.
5. Protruded enlarged tongue.
6. Bloated face.
7. Thick and short limbs occurs