6.1.2 Chemical Nature of Hormones

All the hormones are organic substances of varying structural complexity. Chemically, they may belong to any of the following categories: steroid hormones, proteinaceous hormones, catecholamine, amino acid derivative, and peptide hormones.

Definition

Chemical Nature of Hormones: All the hormones are organic substances of varying structural complexity. Chemically, they may belong to any of the following categories.

Main Idea

• All hormones are organic substances.
• They vary in structural complexity.
• Chemically, they belong to different categories.
• The main categories are:

Core Concept

• Steroid hormones = from adrenal cortex, testes, ovaries, placenta
• Proteinaceous hormones = from anterior pituitary, pancreas
• Catecholamine = from adrenal medulla
• Amino acid derivative = from thyroid gland
• Peptide hormones = from various sources

Detailed Explanation

Chemical Nature of Hormones

All the hormones are organic substances of varying structural complexity. Chemically, they may belong to any of the following categories.

(a) Steroid Hormones

• The hormones secreted by the adrenal cortex, testes, ovaries and placenta are composed of steroids.
• Examples:
• Cortisone
• Aldosterone
• Testosterone
• Estrogen
• Progesterone

(b) Proteinaceous Hormones

• These are also known as polypeptide or peptide hormones.
• Examples:
• Somatotrophic hormone
• Thyrotrophic hormone
• Gonadotrophic hormones
• These are secreted by the anterior lobe of pituitary gland.
• Insulin hormone is secreted by pancreas.

(c) Catecholamine

- Adrenaline and noradrenaline are secreted by the adrenal medulla.

(d) Amino Acid Derivative

- Thyroxine hormone is secreted by the thyroid gland.

(e) Peptide Hormones

• These include:
• Melanocyte stimulating hormone
• The hormones oxytocin and vasopressin
• Adrenocorticotrophic hormone
• Calcitonin
• Parathormone

Summary Table of Chemical Nature of Hormones

Intermediate Level

Chemical Nature of Hormones

Detailed Classification

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. All hormones are organic substances.
• 2. They vary in structural complexity.
• 3. Chemically, they belong to different categories.
• 4. Steroid hormones are composed of steroids.
• 5. Steroid hormones are secreted by adrenal cortex, testes, ovaries, and placenta.
• 6. Examples of steroid hormones: cortisone, aldosterone, testosterone, estrogen, progesterone.
• 7. Proteinaceous hormones are also known as polypeptide or peptide hormones.
• 8. Proteinaceous hormones are secreted by anterior pituitary and pancreas.
• 9. Examples of proteinaceous hormones: somatotrophic, thyrotrophic, gonadotrophic, insulin.
• 10. Catecholamine hormones are secreted by adrenal medulla.
• 11. Examples of catecholamine: adrenaline and noradrenaline.
• 12. Amino acid derivative hormone is secreted by thyroid gland.
• 13. Example of amino acid derivative: thyroxine.
• 14. Peptide hormones include melanocyte stimulating hormone, oxytocin, vasopressin, ACTH, calcitonin, parathormone.
• 15. Different hormones have different chemical structures.
• 16. Their structure determines how they work.
• 17. All hormones are organic substances.
• 18. Hormones are essential for body functions.
• 19. Hormones work through receptors.
• 20. Hormones regulate metabolic functions.

Remember

• - Steroid hormones = from adrenal cortex, testes, ovaries, placenta
• - Proteinaceous hormones = from anterior pituitary, pancreas
• - Catecholamine = from adrenal medulla
• - Amino acid derivative = from thyroid gland
• - Peptide hormones = from various sources
• - Examples = cortisone, aldosterone, testosterone, estrogen, progesterone
• - Examples = somatotrophic, thyrotrophic, gonadotrophic, insulin
• - Examples = adrenaline, noradrenaline
• - **Example** = thyroxine
• - Examples = melanocyte stimulating hormone, oxytocin, vasopressin, ACTH, calcitonin, parathormone

Common Mistakes

• 1. Confusing the categories of hormones — Steroid, proteinaceous, catecholamine, amino acid derivative, peptide.
• 2. Mixing up the sources — Steroid: adrenal cortex, gonads; proteinaceous: pituitary, pancreas; catecholamine: adrenal medulla; amino acid derivative: thyroid.
• 3. Forgetting the examples — Cortisone, insulin, adrenaline, thyroxine, etc.
• 4. Thinking all hormones are proteins — They belong to different chemical categories.
• 5. Mixing up the types — Steroid vs. proteinaceous vs. peptide.
• 6. Forgetting the role of the adrenal cortex — Secretes steroid hormones.
• 7. Confusing catecholamine and amino acid derivative — Catecholamine: adrenaline; amino acid derivative: thyroxine.
• 8. Believing hormones are not organic — All hormones are organic substances.
• 9. Thinking hormones have the same structure — They vary in structural complexity.
• 10. Mixing up the peptide hormones — Melanocyte stimulating hormone, oxytocin, vasopressin, ACTH, calcitonin, parathormone.

Quick Revision

All the hormones are organic substances of varying structural complexity. Chemically, they may belong to any of the following categories. (a) Steroid-hormones: The hormones secreted by the adrenal cortex, testes, ovaries and placenta are composed of steroids e.g., cortisone, aldosterone, testosterone, estrogen, progesterone. (b) Proteinaceous hormones: These are also known as polypeptide or peptide hormones. Somatotrophic, thyrotrophic and gonadotrophic hormones are secreted by the anterior lobe of pituitary gland and insulin hormone is secreted by pancreas. (c) Catecholamine: Adrenaline and noradrenaline are secreted by the adrenal medulla. (d) Amino acid derivative: Thyroxine hormone is secreted by the thyroid gland. (e) Peptide Hormones: These include melanocyte stimulating hormone, the hormones oxytocin and vasopressin, adrenocorticotrophic hormone, calcitonin and parathormone.

60-Second Revision

• Steroid hormones = from adrenal cortex, testes, ovaries, placenta
• Proteinaceous hormones = from anterior pituitary, pancreas
• Catecholamine = from adrenal medulla
• Amino acid derivative = from thyroid gland
• Peptide hormones = from various sources
• Examples = cortisone, aldosterone, testosterone, estrogen, progesterone
• Examples = somatotrophic, thyrotrophic, gonadotrophic, insulin
• Examples = adrenaline, noradrenaline
• Example = thyroxine
• Examples = melanocyte stimulating hormone, oxytocin, vasopressin, ACTH, calcitonin, parathormone
• Warning: Hormones belong to different chemical categories based on their structure

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• 6. Endocrine System of Man

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• 6.2 ENDOCRINE SYSTEM OF MAN

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