What is the primary hormone secreted by the thyroid?

Question

What is the primary hormone secreted by the thyroid??  
A. Oxytocin  
B. TSH  
C. Adrenaline  
D. T4

Accepted Answer

Correct Answer: (D)T4. 
Rationale: The primary hormone secreted by the thyroid gland is T4 (thyroxine).The thyroid gland is an endocrine organ located in the anterior neck whose primary function is the production of thyroid hormones. The two major hormones it produces are thyroxine (T4) and triiodothyronine (T3). These hormones regulate metabolic rate, energy utilization, growth, and development throughout the body. Among the answer choices given, only T4 is directly synthesized and released by thyroid tissue, which makes it the correct physiological response to the question.A) OxytocinOxytocin is not produced by the thyroid gland. It is synthesized in the hypothalamus and transported to the posterior pituitary gland, where it is stored and released into the bloodstream. Its major physiological roles include stimulating uterine contractions during labor and promoting milk ejection during breastfeeding. Oxytocin also plays a role in social bonding and maternal behaviors.From a physiological perspective, oxytocin belongs to the group of neurohormones involved in reproductive and behavioral functions, not metabolic regulation. It does not influence thyroid hormone synthesis, iodine metabolism, or basal metabolic rate. Because it originates from the hypothalamic–pituitary system and has no functional or anatomical connection to the thyroid gland, oxytocin is an incorrect answer.B) TSH (Thyroid-stimulating hormone)Thyroid-stimulating hormone is secreted by the anterior pituitary gland, not the thyroid gland. Its function is to regulate thyroid activity by stimulating the thyroid follicles to absorb iodine and synthesize T4 and T3. TSH is therefore a controlling or regulatory hormone rather than a product of the thyroid itself.Clinically, TSH is often measured to assess thyroid function because its level changes in response to circulating thyroid hormone concentrations. However, its site of production remains the pituitary gland. Since the question asks which hormone is produced by the thyroid gland, TSH cannot be the correct answer.C) Adrenaline (epinephrine)Adrenaline is produced by the adrenal medulla, which is part of the adrenal glands located on top of the kidneys. It is a key hormone of the sympathetic nervous system and plays a major role in the body’s response to stress by increasing heart rate, blood pressure, and blood glucose levels.Although adrenaline influences metabolism and energy availability, it is synthesized from tyrosine in chromaffin cells of the adrenal medulla, not in thyroid tissue. It has no direct biosynthetic pathway, storage mechanism, or secretion process involving the thyroid gland. Therefore, adrenaline is unrelated to thyroid hormone production and is an incorrect choice.D) T4 (thyroxine)T4 is the principal hormone produced and secreted by the thyroid gland. It is synthesized by thyroid follicular cells through the iodination of tyrosine residues within thyroglobulin. Each molecule of T4 contains four iodine atoms, which is why adequate dietary iodine is essential for normal thyroid function.T4 accounts for more than 90 percent of the hormone output of the thyroid gland. In peripheral tissues such as the liver, kidneys, and skeletal muscle, T4 is converted into T3, the more biologically active form. Together, these hormones regulate basal metabolic rate, oxygen consumption, heat production, cardiovascular activity, and normal growth and neurological development, particularly in infants and children.Conclusion:The thyroid gland’s primary endocrine function is the production of thyroid hormones that regulate metabolism and growth. Oxytocin is produced by the hypothalamus and released by the posterior pituitary, TSH is produced by the anterior pituitary to regulate thyroid activity, and adrenaline is produced by the adrenal medulla as part of the stress response. Only T4 is synthesized and secreted by thyroid follicular cells.For this reason, T4 is the correct and most medically accurate answer to the question.

What is the primary hormone secreted by the thyroid?

A
Oxytocin

B
TSH

C
Adrenaline

D
T4

The primary hormone secreted by the thyroid gland is T4 (thyroxine).

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What is the primary hormone secreted by the thyroid?

A Oxytocin B TSH C Adrenaline D T4

The primary hormone secreted by the thyroid gland is T4 (thyroxine).

Topic Flashcards

Mini Quiz

Related Questions

A
Oxytocin

B
TSH

C
Adrenaline

D
T4