Question

In humans, increased thyroxine production results ¡n
A. Increased metabolism
B. Decreased metabolism
C. Dwarfism
D. Cretinism

Answer 1

The thyroid is an endocrine gland. It is a bilobed structure located in the neck region, below the larynx on each side of the upper trachea. It is the largest endocrine in the human body. It secretes two hormones- thyroxine and calcitonin.

Complete answer:
The follicular cells of thyroid gland secrete two hormones namely triiodothyronine and thyroxine or tetraiodothyronine. The parafollicular cells of thyroid gland secrete a hormone called thyrocalcitonin. Iodine is an essential element for the normal synthesis of thyroid hormones. Thyroid hormone is essential for the growth and maturation of many target tissues, including the brain and skeleton. Thyroxine regulates the rate of cellular oxidation. It controls growth and development, ossification of the bones, body temperature, mental development. This is the reason, hormones of the thyroid gland are often called the major metabolic hormones.
The condition of oversecretion of thyroxine is called hyperthyroidism. This condition causes a noticeable increase in the metabolic rate, increase in heartbeat, shortness of breath and the eyes protrude out together with goitre in the neck.

Thus, option A. Increased metabolism is the correct answer.

Additional information:
Under Secretion of thyroxine is called hypothyroidism. It causes enlargement of the thyroid gland, visible as simple goitre. Less secretion may also cause Poor body growth (dwarfism) and mental retardation.

Note:
Excessive secretion of thyroxine causes increases in metabolism such as increased metabolic rate, rapid heartbeat, shortness of breath and the eyes protrude out together with goitre in the neck.