Endocrine system

Endocrine system

It includes endocrine or ductless glands.Their secretion is known as hormones.Different type of hormones are :
1.Steroids : e.g.,estradiol,testosterone,androsterone,aldosterone,cortisol,and cortisone.
2.Peptides : insulin,glucagon,pituitary hormones,parathormone and relaxin.
3.Amino acid derivatives : Adrenaline,noradrenaline and thyroid hormones.Pituitary gland is also known as master gland.

Some Endocrine Glands :
Thyroid Gland : It is the largest endocrine gland and situated in neck region.It is the pace setter of the endocrine system .It secretes thyroxine.
Gonads : It secretes steroid hormones.
Ovarian hormones(Oestrogens): It helps in the development of primary and secondary sexual characters.
Testicular Hormones(Androgens) : These are produced by Leydig's cells of testes.It stimulate growth ,maturation and maintenance of male gonads and development of secondary sexual characters,e.g. testosterone,androsterone,etc.

Effect of Deficiency and Excess of Hormones

Thyroxine Secretion : Lower secretion causes cretinism (young),Hashimoto's disease and myxoedema in adult.Higher secretion causes exophthalmic goitre.Lack of iodine in the diet causes goitre.
Parathomone Secretions : Lower secretion causes tetany,Higher secretion causes neurofibromatosis.
Growth stimulating Hormones Secretions : Lower secretion caused Dwarfism in young,Higher secretion caused gigantism in adult.LTH helps formation of crop milk in birds.Let down reflax or milk ejection response.
Insulin Secretion : Lower secretion leads ti diabetes mellitus.Aldosterone hypersecretion causes Conn's syndrome.Cortisol oversecretion causes Cushing's syndrome.