Hormones: Definition, What They Are, Function, Types, Causes, Symptoms, Treatment

What Are Hormones?

Hormones are chemical messengers synthesised from the endocrine glands. They travel in blood to reach target organs and tissues to control various physiological processes to maintain homeostasis.

Types of Hormones

The types of hormones include:

Peptide Hormones

• Consisting of amino acids.

• Examples: Insulin, glucagon, and growth hormone.

Steroid Hormones

• Consisting of cholesterol.

• Examples: Cortisol, aldosterone, estrogen, and testosterone.

Amino Acid-Derived Hormones

• Consisting of single amino acids.

• Examples: Thyroxine, epinephrine, and norepinephrine.

Glycoprotein Hormones

• Protein hormones with carbohydrate groups.

• Examples: Follicle-stimulating hormone, luteinizing hormone.

Functions of Hormones

The functions of hormones include:

Regulation of Metabolism

• Insulin and glucagon act on the levels of blood sugar.

• Thyroid hormones act on metabolic rate.

Growth and Development

• Growth hormone acts on growth in the tissues.

• Estrogen and testosterone act as sex hormones in reproductive growth and development.

Homeostasis

• Aldosterone holds homeostasis in sodium and potassium balance.

• Antidiuretic hormone maintains the balance of water in the body.

Stress Response

• Cortisol and adrenaline control the stress response in the body.

Reproduction

• Hormones like FSH and LH maintain the menstrual cycle in females and spermatogenesis in males.

Major Endocrine Glands and Hormones

The major endocrine glands are:

Pituitary Gland

• Also known as the master gland.

• Produces hormones like growth hormone, prolactin, and oxytocin.

Thyroid Gland

• Produces thyroid hormones T3 and T4

• Maintain the metabolic rate.

Adrenal Glands

• They secrete hormones like cortisol, adrenaline, and aldosterone.

Pancreas

• Produces hormones like insulin and glucagon

• Regulate blood sugar levels.

Gonads

• Ovaries in females produce oestrogen and progesterone

• Testes in males produce testosterone.

Mechanisms of Hormone Action

The mechanism of hormone action include:

Feedback Mechanism

• Negative feedback loops maintain homeostasis.

• For example, the level of the thyroid hormone is maintained by the hypothalamic-pituitary axis.

Response to Stimuli

• Stress, increased blood sugar, change in ion concentration, etc can lead to the secretion of hormones.

Hormone Action and Receptors

Hormones exert their action by combining with specific receptors on target cells.

Cell Surface Receptors

• These are for peptide hormones and amino acid-derived hormones.

• The receptors trigger an intracellular cascade after binding between the hormone and the receptor.

Intracellular Receptors

• These belong to steroid and thyroid hormones.

• They reside in the cell, and the hormones diffuse through the plasma membrane

• They elicit their response, mostly changes in gene expression, upon binding.

Important Hormones

Some important hormones include:

Roles of Hormones in the Body

Hormones carry out a range of crucial roles in the body, which include:

• Food metabolism

• Growth and development

• Thirst and hunger regulation

• Thermoregulation

• Mood and cognition

• Sex development and reproduction

Hormonal Diseases

The hormonal diseases are brought about by disorders or malfunctioning of the endocrine glands, similar to that of the hypothalamus, adrenal, and pituitary glands. Some of the well-known diseases include

• Hyperthyroidism: Too much production of thyroid hormone occurs.

• Osteoporosis: Condition characterized by reduced bone mass due to hormonal imbalance.

• Diabetes: Abnormality in insulin production or action which misregulates the sugar level in the blood.

Hormones NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Types of hormones

• Major glands and the their hormones

• Mechanism of hormone action

Practice Questions for NEET

Q1. Which of the following are the types of Chemical hormones?

1. Proteins, steroids & biogenic amines

2. Proteins only

3. Steroids only

4. Biogenic amines only

Correct answer: 1) Proteins, steroids & biogenic amines

Explanation:

Chemically, hormones are composed of proteins, steroids, and biogenic amines. Protein hormones are composed of amino acids and include examples such as insulin and growth hormone. Steroid hormones are derived from cholesterol and include examples such as testosterone and cortisol. Biogenic amine hormones are derived from amino acids and include examples such as epinephrine and serotonin.

Hence, the correct answer is option 1) Proteins, steroids & biogenic aminesis.

Q2. Proteins perform many physiological functions. For example, some functions as enzymes. Which of the following represents an additional function that some proteins discharge?

1. Antibiotics

2. Pigment conferring colour to skin

3. Pigments making colours of flowers

4. Hormones

Correct answer: 4) Hormones

Explanation:

Antibiotics that contain enzymes do not possess proteins, but many antibodies might not have proteins or enzymes. Moreover, pigments are not proteins. Hormones can be categorized chemically as either proteins or steroids. Except for sex hormones and those derived from the adrenal cortex, every hormone in the human body is a protein or a protein derivative.

Hence, the correct answer is Option 4) Hormones.

Q3. Name a peptide hormone which acts mainly on hepatocytes, and adipocytes and enhances cellular glucose uptake and utilization.

1. Insulin

2. Glucagon

3. Secretin

4. Gastrin

Correct answer: 1) Insulin

Explanation:

Insulin - Insulin is a peptide hormone, which plays a major role in the regulation of glucose homeostasis. Insulin acts mainly on hepatocytes and adipocytes (cells of adipose tissue) and enhances cellular glucose uptake and utilization

Hence, the correct answer is option 1) Insulin.

Also Read:

• MCQs on Introduction to Endocrine System

• Pituitary Gland

• Adrenal Gland

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