For therapeutic use, growth hormone is obtained from:

Correct Answer: A

Rationale: Growth hormone used for therapeutic purposes is obtained through a process called recombinant DNA technology. This method involves inserting the gene that codes for human growth hormone into a bacterial or yeast cell, which then produces the hormone in large quantities. This synthetic growth hormone is identical to the naturally occurring hormone in the body and is safe and effective for therapeutic use. Harvesting growth hormone from human cadaver pituitaries poses a risk of disease transmission, while obtaining it from porcine pituitaries raises concerns about potential immune reactions. Chemical synthesis may not yield a biologically active form of the hormone. Therefore, the most reliable and safe source of therapeutic growth hormone is through the recombinant DNA technique.

Correct Answer: A

Rationale: The metabolic rate of the brain is not significantly affected by thyroxine. Thyroxine mainly influences the metabolic rate of organs with high energy demands such as the heart, liver, and skeletal muscle. Thyroxine increases the metabolic rate by stimulating the production of enzymes involved in energy production and consumption. However, the brain has a relatively stable metabolic rate that is not significantly influenced by changes in thyroid hormone levels.

Correct Answer: D

Rationale: Triiodothyronine (T3) is preferred over thyroxine (T4) in the treatment of Myxoedema coma, which is a severe form of hypothyroidism that can lead to decreased mental function, hypothermia, and even coma. T3 has a faster onset of action and is more potent than T4, making it the preferred choice in emergency situations like myxoedema coma where rapid correction of thyroid hormone levels is crucial to prevent serious complications. In contrast, in conditions like endemic goiter, cretinism, and papillary carcinoma of thyroid, where long-term maintenance therapy is needed, thyroxine (T4) is usually the preferred choice because of its longer half-life and stability of serum levels over time.

Correct Answer: D

Rationale: In this scenario, the correct answer is D) All of the above. The rationale behind this is that overtreatment with any of the thyroid inhibitors listed (Lugol's iodine, Radioactive iodine, and Carbimazole) can lead to enlargement of the thyroid, a condition known as goiter. Lugol's iodine is a solution containing molecular iodine and potassium iodide, which can cause goiter if used in excess. Radioactive iodine, often used in the treatment of hyperthyroidism, can also lead to goiter if the dosage is too high. Carbimazole, a medication used to treat hyperthyroidism, can cause goiter as a side effect when overused or not properly monitored. To understand why the other options are incorrect, we can look at their individual mechanisms. Lugol's iodine and radioactive iodine are both forms of iodine that can affect thyroid function, but they are not the only substances that can cause goiter through overtreatment. Carbimazole, as mentioned earlier, is a medication that can also result in goiter if misused. In an educational context, it is crucial for students to grasp the potential consequences of overtreatment with thyroid inhibitors, as this knowledge is essential for healthcare professionals working with patients with thyroid disorders. Understanding the side effects and proper dosages of these medications is vital for providing safe and effective care to individuals with thyroid conditions.

Correct Answer: A

Rationale: Propranolol, a non-selective beta-blocker, is often used in hyperthyroidism as short-term symptomatic therapy to help manage symptoms such as tachycardia, tremors, and anxiety until the effect of carbimazole, an anti-thyroid medication, begins to take effect. Propranolol does not directly treat the underlying thyroid condition but can provide relief from some of the uncomfortable symptoms associated with hyperthyroidism. Once carbimazole starts to control the overproduction of thyroid hormones, the need for propranolol may decrease or even be eliminated. It is not typically used as long-term maintenance therapy or in cases where other anti-thyroid medications like carbimazole are effective.