Thyroid Gland: What It Is, Causes, Symptoms, Treatment

What Is the Thyroid Gland?

The thyroid is an endocrine gland, shaped like a butterfly, and it is located at the base of the neck. It produces hormones that regulate metabolic processes, growth, and development.

It plays a very vital role in the endocrine system in the maintenance of energy levels of the body, protein synthesis, and health. Normal thyroid function seems essential for normal growth and development and is hence very vital for human health.

Anatomy of the Thyroid Gland

The anatomy of the thyroid gland is discussed below:

Location and Structure

• Located at the front of the neck, just below the larynx (Adam's apple).

• Two lateral lobes, connected by an isthmus.

Parts of the Thyroid

It comprises the following parts:

• Lobes: Right and left lobes

• Isthmus: Thin band of tissue connecting the two lobes

• Follicles: Spherical units storing thyroid hormones

• Blood Supply: From the superior and inferior thyroid arteries

• Innervation: Receives nerve impulses from the sympathetic nervous system.

Physiology of the Thyroid Gland

The thyroid gland produces vital hormones and is controlled through a negative feedback loop involving the hypothalamus and pituitary.

Hormone Synthesis

• Thyroxine (T4): Major hormone produced, later converted to T3.

• Triiodothyronine (T3): Active form derived from T4.

• Calcitonin: Concerned with calcium metabolism.

• Iodine is considered an 'essential element' for the synthesis of T3 and T4.

Regulation (Feedback Mechanism)

• TRH is released from the hypothalamus

• Stimulates pituitary to release TSH.

• TSH in turn causes the thyroid to produce T3 and T4.

• Negative feedback maintains hormone balance

Functions of Thyroid Hormones

Thyroid hormones have effects on many parts of the body. These include:

Metabolism

• They elevate the basal metabolic rate

• Enhance the rate at which the body makes energy from nutrients.

Growth and Development

• These hormones are crucial in the normal growth of children.

• It is necessary for brain development.

Body Temperature Regulation

• They aid in the maintenance of body temperature through an effect on the amount of heat given off by cells.

Effects On Other Systems

• Cardiovascular: Controls heart rate and the force of contraction.

• Nervous System: Affects mood, thought processes, and overall mental status.

• Reproductive System: Necessary for normal functioning and health of reproductive structures.

Disorders of the Thyroid Gland

Diseases of the thyroid gland are of such a major impact on health and well-being, and so must be correctly diagnosed and treated.

Hypothyroidism

• Causes: Hashimoto's thyroiditis, lack of iodine.

• Symptoms: Fatigue, weight gain, cold intolerance, depression

• Diagnosis: Blood tests with high TSH and low T3/T4.

• Treatments: Hormone replacement.

Hyperthyroidism

• Causes: Graves' illness, thyroid nodules, excessive iodine.

• Symptoms: Loss of weight, rapid heartbeats, intolerance to heat, anxiety.

• Diagnosis: Blood tests with low TSH and high T3/T4.

• Treatments: Thyroid-reducing drugs, radioactive iodine therapy, or surgical operation.

Goiter

• Causes: Iodine deficiency, thyroid inflammation

• Symptoms: Neck swelling, difficulty in swallowing or breathing.

• Diagnosis: Physical examination, ultrasonography, thyroid function tests.

• Treatment: Supplements containing iodine, and surgery if required

Nodules And Cancer Of Thyroid

• Types: Benign nodules, papillary carcinoma, follicular carcinoma, medullary thyroid carcinoma, anaplastic carcinoma.

• Diagnosis: Fine-needle aspiration biopsy, ultrasound

• Treatment: Surgical methods, radioactive iodine therapy, radiation therapy, or chemotherapy.

Diagnostic Tests For Thyroid Function

Thyroid disorders require diagnostic testing to evaluate hormone levels and the structure of the gland.

Blood Tests

• TSH

• T3 and T4 levels

Imaging

• Ultrasound:

• Radioactive Iodine Uptake Test

• Fine-needle aspiration biopsy.

Prevention And Management

Thyroid health is maintained through dietary, lifestyle, and medical measures.

• Adequate intake of iodine in the form of iodised salt, seafood and milk products.

• Periodic thyroid function tests, especially when there is a family history of disorders of the thyroid gland.

• One may ensure good thyroid health by maintaining a healthy diet, exercising regularly, and managing stress.

Thyroid Gland NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Thyroid gland hormones and their functions

• Disorders related to Thyroid gland

Practice Questions for NEET

Q1. Which of the following conditions is not linked to deficiency of thyroid hormone?

1. Cretinism

2. Goitre

3. Myxedema

4. Exophthalmos

Correct answer: 4) Exophthalmos

Explanation:

Exophthalmos happens due to hyperthyroidism. Exophthalmos, or bulging of the eyes, is a common symptom of Graves' disease, a form of hyperthyroidism. It occurs due to inflammation and swelling of the tissues and muscles behind the eyes caused by an autoimmune response.

Hence, the correct answer is the option 4) Exophthalmos.

Q2. The hormone which regulates the basal metabolism in our body is secreted from

1. Adrenal cortex

2. Pancreas

3. Pituitary

4. Thyroid

Correct answer: 4) Thyroid

Explanation:

The hormone that oversees the fundamental energy consumption in our body is Thyroxine (T4), produced by the thyroid gland. Within specific organs like the liver and kidneys, T4 transforms into the more potent triiodothyronine (T3), which is crucial for metabolic regulation. These hormones adjust the basal metabolic rate (BMR), the energy expenditure at rest for essential functions such as respiration, blood flow, and cellular activities. The pituitary gland's thyroid-stimulating hormone (TSH) controls thyroxine release, guided by the hypothalamus. They play a pivotal role in growth, development, body temperature management, and overall energy usage.

Hence, the correct answer is option 4) Thyroid.

Q3. Thyroxine has an important role in regulating

1. Blood calcium level

2. Basal metabolic rate

3. Water and electrolyte balance

4. Both 2 and 3

Correct answer: 4) Both 2 and 3

Explanation:

Thyroid hormones are essential in regulating carbohydrate, protein, and fat metabolism. They affect many metabolic pathways and enhance the overall metabolic rate and energy expenditure of the body. In detail, thyroid hormones stimulate lipolysis, which is the breakdown of fats, and promote the synthesis of proteins and carbohydrates. They also maintain water and electrolyte balance, thus affecting hydration and cellular function. Dysregulation of thyroid hormones brings about some major metabolic disorders that affect weight and energy levels.

Hence, the correct answer is option (4) Both 2 and 3.

Also Read:

• MCQs on Thyroid Gland

• Mechanism of Hormone Action

• Parathyroid Gland

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