This set of Molecular Endocrinology Multiple Choice Questions & Answers (MCQs) focuses on “Metabolic Role of Thyroid Hormones”.
1. What is the name of the disease that affects skeletal muscles as a side effect of hyperthyroidism?
a) Thyrotoxic myopathy
b) Myopathic syndrome
c) Goiter
d) Iodine myopathy
View Answer
Explanation: In cases of hyperthyroidism, the catabolic reaction in skeletal muscle is often so extreme with muscle fatigue as a major symptom. This disease condition is called thyrotoxic myopathy. TM is also known as hyperthyroid myopathy and is one of the myopathies contributing to muscle weakness and breakdown of muscle tissue.
2. What is the role of thyroid hormones in fatty acid metabolism in the adipose tissues?
a) Decreases lipolysis
b) Increases lipolysis
c) Increases lipogenesis
d) Maintains lipogenesis
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Explanation: Thyroid hormones in adipose tissue increase lipolysis, thereby raising plasma free fatty acids (FFA). By enhancing the activities of malic enzymes, ATP, citrate lyase and G-6-PD, they can promote lipogenesis at the same time.
3. What is the name of the mechanism in which antithyroid affects are expressed by iodide?
a) Jod-Basedow effect
b) Lesh- Nyhan syndrome
c) Wolff-Chaikoff effect
d) Maple Syrup Urine disease
View Answer
Explanation: Iodide exerts antithyroid effects at high serum concentrations exceeding 30 μg/dl and sometimes even produces transient goitre. This condition is referred to as Wolff-Chaikoff effect. Iodine plays a major role in the synthesis of thyroid hormones in the follicular lumen. Tyrosines are iodinated to from MIT and DIT which in turn couples to form T4, T3 and Reverse T3.
4. Diabetes mellitus is aggravated by co-existing thyrotoxicosis or by thyroid hormone administration.
a) True
b) False
View Answer
Explanation: Thyroid hormones increase the rate at which glucose from the intestine is absorbed. Decreased glucose tolerance can also be caused by the acceleration of insulin degradation. There is an underlying rise in hepatic gluconeogenesis, rapid absorption of gastrointestinal glucose, and likely increased resistance to insulin. Indeed, latent diabetes can be unmasked by thyrotoxicosis.
5. A decline in glycogen storage in the liver is triggered by thyroid hormones.
a) True
b) False
View Answer
Explanation: A reduction in glycogen storage in the liver and in the myocardium and skeletal muscles is triggered by thyroid hormones. Thyroid hormones, at the same time, enhance hepatic gluconeogenesis by increasing the activity of pyruvate carboxylase and PEP carboxykinase.
6. Which among the following is an example of thiocarbamide antithyroid drug?
a) Periodate
b) Methimazole
c) Tolbutamide
d) Colchicine
View Answer
Explanation: Methimazole which is otherwise known as tapazole is an example of thiocarbamides. Thiocarbamides block iodide oxidation to active iodine. They inhibit the MIT iodination mechanism. They also block the coupling reaction and can inhibit thyroglobulin synthesis.
7. What is the role of thyroid hormones in oxygen consumption of cells?
a) Increases oxygen consumption
b) Decreases oxygen consumption
c) Prevents oxygen consumption
d) Reduces oxygen coefficient
View Answer
Explanation: Thyroid hormones greatly increase the oxygen coefficient and oxygen intake of nearly all metabolically active tissues. The brain, testicles, uterus, lymph nodes, spleen and anterior pituitary are exceptions.
8. Which thyroid hormone is necessary for the conversion of carotene to vitamin A?
a) ‘Reverse’ T3
b) Tri-iodothyronine
c) Parathormone
d) Thyroxine
View Answer
Explanation: The hepatic conversion of carotene to vitamin A requires thyroxine. In hypothyroidism, carotene concentration in the bloodstream is responsible for the yellowish color of the face. Vitamin A, in turn, has been shown to regulate the metabolism of thyroid hormones and inhibit the secretion of thyroid-stimulating hormone (TSH) by controlling the expression of the TSH-β gene.
9. Which among the following is an aminobenzene antithyroid drug?
a) Tolbutamide
b) Periodate
c) Colchicine
d) Methimazole
View Answer
Explanation: Tolbutamide is an example of aminobenzene antithyroid drug. The conversion of iodide to active iodine is inhibited by aminobenzene and thus prevents thyroperoxidase. It also lowers reactions of iodination and coupling.
10. Vinblastin belongs to which class of antithyroid drugs?
a) Aminobenzenes
b) Inhibitory drugs
c) Thiocarbamides
d) Monovalent anions
View Answer
Explanation: Vinblastin belongs to the inhibitory drugs that prevents the release of thyroid hormones. They inhibit the development of microtubules and microfilament thyroid hormones in apical thyroid cells. Vinblastine is a chemical analogue of vincristine, an alkaloid derived from the Vinca rosea (Catharanthus roseus) periwinkle plant of Madagascar, from which it derived its name.
Sanfoundry Global Education & Learning Series – Molecular Endocrinology.
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