Problem 128 - Objective Biology for NEET

Question

Assertion: Failure of secretion of thyroid gland hormones from childhood causes cretinism disease. Reason: Thyrotropin hormone maintains BMR and promotes the growth of body tissues.

Step-by-Step Solution

Answer

The assertion is true but the reason is incorrect as it fails to explain the assertion correctly. It's the lack of thyroid hormones, not thyrotropin that causes cretinism disease.

Step 1 Understanding the roles of hormones

First, let's consider the role of thyroid hormones. These hormones, which include thryoxine (T4) and triiodothyronine (T3), play a major role in metabolism, growth and development of human body. A deficiency in these hormones, especially from an early age, can lead to disorders such as cretinism, characterized by stunted physical and mental growth. Hence, the assertion is valid.

Step 2: Understanding the role of Thyrotropin

Next, let's look at thyrotropin. This hormone, also known as thyroid-stimulating hormone (TSH), is secreted by the pituitary gland and regulates the production of thyroid hormones by the thyroid gland. It indeed maintains BMR and promotes the growth by maintaining the rate of metabolism, but is not directly responsible for these functions. In fact, it is the deficiency of the thyroid hormones which produce the adverse effects rather than the thyrotropin hormone itself. So, the reason does not provide a proper explanation to the assertion.

Step 3: Finishing the exercise

From our analysis we can conclude that while the assertion is correct, the reason provided does not justify the assertion correctly. Thyrotropin, while indeed associated with BMR and tissue growth, is not the hormone whose deficiency causes cretinism disease, but rather stimulates the thyroid gland to produce the hormones that if deficient can cause the disease. Therefore, the assertion holds true independently, and the reason is correct but doesn't explain the assertion.

Key Concepts

Thyroid Hormones

Thyroid hormones are crucial compounds in the human body that help regulate various key functions. The primary hormones produced by the thyroid gland are thyroxine (T4) and triiodothyronine (T3). These hormones play a pivotal role in metabolic processes. They control how quickly the body uses energy, synthesizes proteins, and how sensitive the body is to other hormones.

• Thyroid hormones are important for growth and development, particularly in children. They ensure that bones grow properly and support the brain's development.
• A deficiency of these hormones, especially during childhood, can lead to a condition known as cretinism, which causes stunted physical and mental growth.

Proper functioning of these hormones is vital for maintaining overall health and well-being. They affect almost every cell in your body, influencing metabolism, heart rate, muscle strength, digestion, and more.

Cretinism

Cretinism is a medical condition in children that arises due to a deficiency of thyroid hormones. It is typically diagnosed when a child shows signs of impaired growth and development.

• Cretinism is characterized by slow physical growth, a delayed mental and cognitive development, and other physiological abnormalities.
• Symptoms may include lethargy, feeding problems, and significant delays in developmental milestones such as sitting, standing, and walking.

To prevent cretinism, it is crucial to identify and treat thyroid hormone deficiencies early on. Early therapeutic intervention can lead to better outcomes, helping children achieve closer to normal physical and mental development.

Thyrotropin (TSH)

Thyrotropin, also known as thyroid-stimulating hormone (TSH), is an important hormone produced by the pituitary gland. It plays a central role in regulating the production of thyroid hormones by the thyroid gland.

• TSH signals the thyroid gland to produce more T4 and T3 when their levels are low in the bloodstream.
• This hormone is crucial for maintaining a healthy basal metabolic rate (BMR) and supporting the body's growth and energy utilization processes.

While TSH triggers the production of thyroid hormones, it is not directly responsible for maintaining metabolism or growth. These activities are primarily driven by T4 and T3, the hormones secreted by the thyroid gland. Adequate levels of TSH ensure that the metabolism operates smoothly and that there is sufficient energy for growth and repair.