**Core Concept:** Hormones are chemical messengers produced by the endocrine system that regulate various physiological processes in the body. During stress, the hypothalamic-pituitary-adrenal (HPA) axis gets activated, leading to the release of stress hormones.

**Why the Correct Answer is Right:** Cortisol is a hormone released by the adrenal glands in response to stress. It plays a crucial role in maintaining homeostasis by modulating glucose levels, immune system function, and blood pressure. The HPA axis, a neuroendocrine feedback loop, controls cortisol release.

**Why Each Wrong Option is Incorrect:**

A. This option does not represent a stress hormone.
B. This option is not a primary stress hormone, unlike cortisol.
C. This option is not a stress hormone, as it is related to thyroid function.
D. This option is not a stress hormone, as it is related to parathyroid hormone (PTH) which regulates calcium levels.

**Clinical Pearl / High-Yield Fact:** High-level cortisol secretion can lead to the development of Cushing's syndrome, a condition characterized by obesity, muscle weakness, and skin discoloration.

**Correct Answer:** .

**Why the Correct Answer is Right:** Cortisol is the primary stress hormone released in response to stress. It is produced by the adrenal cortex and acts on various organs to maintain homeostasis.

**Why Each Wrong Option is Incorrect:**

A. This option is not related to cortisol or stress response.
B. This option is not a primary stress hormone, unlike cortisol.
C. This option is not a stress hormone, as it is related to thyroid function and not cortisol.
D. This option is not a stress hormone, as it is related to parathyroid hormone (PTH) which regulates calcium levels, not cortisol.

**Core Concept:** Stress hormones are released by the hypothalamus, pituitary gland, and adrenal cortex in response to perceived threats or challenges to maintain homeostasis. Cortisol acts on various target organs to regulate glucose, immune response, and blood pressure, among other functions.