Absence of thyroid hormone would result in a. increased heart rate and increased force of heart contraction, b. depression of the CNS and lethargy, c. exophthalmos, d. high metabolic rate.

Verified step by step guidance

1. Step 1: Understand the role of thyroid hormones in the body. Thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), are crucial for regulating metabolism, heart rate, and the central nervous system (CNS).
2. Step 2: Analyze each option in the context of thyroid hormone absence. Consider how the lack of these hormones would affect the body's systems.
3. Step 3: Evaluate option (a): Increased heart rate and increased force of heart contraction. Normally, thyroid hormones increase heart rate and force of contraction, so their absence would likely decrease these functions.
4. Step 4: Evaluate option (b): Depression of the CNS and lethargy. Thyroid hormones stimulate the CNS, so their absence could lead to depression of the CNS and feelings of lethargy.
5. Step 5: Evaluate options (c) and (d): Exophthalmos and high metabolic rate. Exophthalmos is associated with hyperthyroidism, not absence of thyroid hormone. A high metabolic rate is also linked to the presence of thyroid hormones, so their absence would likely result in a lower metabolic rate.

Key Concepts

Thyroid Hormones

Thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), are crucial for regulating metabolism, growth, and development. They influence various physiological processes, including heart rate, energy expenditure, and the functioning of the central nervous system. An absence of these hormones can lead to significant metabolic and physiological changes.

Hypothyroidism

Hypothyroidism is a condition characterized by insufficient production of thyroid hormones. This deficiency can lead to symptoms such as fatigue, weight gain, depression, and a slowed heart rate. Understanding hypothyroidism is essential for recognizing the effects of low thyroid hormone levels on the body, including the central nervous system and overall metabolism.

Metabolic Rate

Metabolic rate refers to the rate at which the body converts food into energy. Thyroid hormones play a significant role in regulating this rate; a deficiency can lead to a decreased metabolic rate, resulting in weight gain and lethargy. Recognizing the relationship between thyroid function and metabolic rate is vital for understanding the consequences of hormone absence.