[Biology Class Notes] on Multinodular Goiter Pdf for Exam

Introduction

Various hormones in our body regulate cellular functions. These hormones are made by the glands in our body. Two types of glands endocrine and exocrine manufacture various hormones that control the physiological functions of the body. Hormones are non-nutrient chemicals produced in traces. They are intercellular messengers that act on the target tissue and the body similarly responds to these messengers as the nerve impulses. Only, the response from a hormone is much slower. Any deficiency or exceeding levels of the hormone in the body causes illnesses. One of these is Multinodular Goiter.

What is a Multinodular Goiter?

[]

Multinodular Goiter is a condition that arises from the malfunctioning of the thyroid gland. In this condition, multiple lumps, also known as nodules form over the gland. The nodules may be visible or may only be seen in an examination or scan. It may be asymptomatic, meaning, no signs can be seen and may remain in that state. Or it may be non- functional, or it may even be visible or cause serious implications like thyroid cancer. This condition of formation of nodules is a common thyroid disorder.

Thyroid disorders arise from the malfunctioning of the thyroid gland which is one of the many endocrine glands in the body. This gland is located around the sides of the trachea and is a small butterfly-shaped gland. Major hormones that the thyroid gland synthesizes are Tetraiodothyronine or thyroxine (T4), triiodothyronine (T3), and a protein hormone, thyrocalcitonin (TCT).

T3 and T4 together regulate the metabolic activity of the body. They mostly control the metabolism of carbohydrates, fats, and proteins. They regulate the formation of RBC and also maintain the water and electrolyte balance in the body. TCT, on the other hand, regulates the blood calcium levels.

Causes of Multinodular Goiter

When a part or whole of the thyroid gland increases in size it leads to a condition called a goitre. And when multiple lumps or nodules form on the thyroid gland it is known as multinodular goitre. Nodules occur when the different parts of the thyroid gland grow at a different rate. Common causes of multinodular goitre are as follows-

• Deficiency of Iodine

• Biosynthetic defects

• Elevated levels of TSH

• Effect of smoking, stress, certain drugs

• Heredity

• Autoimmune diseases like- Hashimoto’s thyroiditis or Grave’s disease

• Genetic defects leading to thyroid dysfunction

• Sex- more common in women

• Age- Older people are at higher risk of getting goitre

• Nodular disease

Iodine is an essential element which regulates the synthesis of thyroid hormone at a regular rate. Certain genetic defects and deficiency of iodine impact the synthesis of thyroid hormone. When the hormone produced in lower quantities than the required rate, TSH or thyroid-stimulating hormone synthesized by the pituitary gland rises. This, in turn, stimulates the growth of thyroid gland so that it can compensate for the reduced levels of hormone synthesized.

Stages in Multinodular Goiter Formation

[]

1. Stimulation

2. Diffusion of Hyperplastic Goiter. Goitre formation is reversible at the stage of the stimulation ceases.

3. Fluctuating stimulations give rise to mixed patterns and areas of active and inactive lobules occur.

4. Active lobules turn vascular and hyperplastic until haemorrhage occurs which causes central necrosis.

5. Necrotic lobules coalesce to form nodules filled with either iodine-free colloid or a mass of new inactive follicles.

6. Continuous repetition of the process leads to the formation of nodular goitre.

Many times, overactive thyroid also causes enlargement of the thyroid resulting in multinodular goitre.

This is also characterized by disordered growth of thyroid cells often clubbed with the gradual development of fibrosis.

Causes are unknown in many cases.

Symptoms of Multinodular Goiter

Multinodular goitre may not show any symptoms. However, a person may feel the node present on the thyroid gland on the neck region. Physical exam, blood test or biopsy can be done to diagnose more accurately. Some of the symptoms of multinodular goitre are as follows-

• Hoarseness

• Difficulty in swallowing

• Difficulty in breathing

• Difficulty in tolerating heat

• Irritability, nervousness

• Faster heart rate and difficulty in sleeping

• Weight loss