Question

Which of the following would be least likely to be affected by a tumor of the pituitary gland? a. cortisol secretion b. thyroid hormone secretion c. lactation d. secretion of epinephrine by the adrenal medulla

Short answer

d. secretion of epinephrine by the adrenal medulla

Step-by-step solution

Understand the Function of the Pituitary Gland

The pituitary gland is often called the 'master gland' because it controls many other hormone glands in the body. It releases hormones that influence various bodily functions, including growth, metabolism, and reproduction.

Identify the Hormones Controlled by the Pituitary Gland

The pituitary gland controls a variety of hormones including: - Adrenocorticotropic hormone (ACTH), which stimulates cortisol secretion.- Thyroid-stimulating hormone (TSH), which influences thyroid hormone secretion.- Prolactin, which is essential for lactation. These functions would be directly affected by a tumor of the pituitary gland.

Analyze the Role of the Adrenal Medulla

The adrenal medulla is responsible for secreting epinephrine and norepinephrine. It functions primarily under the control of the autonomic nervous system rather than the pituitary gland.

Determine the Least Affected Function

Since the adrenal medulla operates independently of the pituitary gland, secretion of epinephrine by the adrenal medulla would be least likely to be affected by a tumor of the pituitary gland.

Key concepts

Cortisol Secretion

Cortisol is a vital hormone that helps the body respond to stress. When the body senses stress, a chain reaction starts. It begins with the hypothalamus releasing corticotropin-releasing hormone (CRH). Next, the pituitary gland steps in and releases adrenocorticotropic hormone (ACTH). ACTH travels through the bloodstream to the adrenal glands, prompting them to produce cortisol.
Cortisol helps in:

• Raising blood sugar levels
• Boosting energy
• Reducing inflammation
• Helping the body manage stress

Without proper cortisol levels, the body might struggle with stress management and maintaining energy levels.

Thyroid Hormone Secretion

The thyroid gland plays a crucial role in metabolism and energy regulation. To function, it needs signals from the pituitary gland. The pituitary gland releases thyroid-stimulating hormone (TSH), which tells the thyroid gland to produce thyroid hormones - primarily thyroxine (T4) and triiodothyronine (T3).
These hormones are essential for:

• Regulating metabolism
• Controlling heart rate
• Maintaining body temperature
• Influencing growth and development

Changes in TSH levels from the pituitary gland can significantly impact thyroid hormone secretion, affecting many body functions.

Lactation

Lactation, or milk production, is directly influenced by the hormone prolactin. The pituitary gland releases prolactin in response to signals from the hypothalamus.
Prolactin is critical for:

• Initiating and maintaining milk production
• Developing breast tissue
• Ensuring the newborn receives nutrition

After childbirth, high prolactin levels ensure a steady milk supply for feeding the infant.

Adrenal Medulla

The adrenal medulla is a part of the adrenal glands, located on top of the kidneys. Unlike other glands controlled by the pituitary, the adrenal medulla responds to signals from the autonomic nervous system. It produces epinephrine (adrenaline) and norepinephrine (noradrenaline) in response to stress.
These hormones help in:

• Increasing heart rate
• Boosting energy
• Increasing blood flow to muscles
• Preparing the body for 'fight or flight' situations

Since it operates independently of the pituitary gland, a pituitary tumor would not generally affect the adrenal medulla's function.