Endocrinology: Steroid Hormones and Regulation

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Questions and Answers

What is the primary precursor for steroid hormone synthesis?

Progesterone

Corticosterone

Testosterone

Cholesterol (correct)

Which of the following hormones is classified as a glucocorticoid?

Cortisol (correct)

Progesterone

Aldosterone

Testosterone

What type of hormone does the zona glomerulosa primarily secrete?

Gonadal steroids

Mineralocorticoids (correct)

Glucocorticoids

Androgens

Which enzyme is essential for glucocorticoid activity?

11beta-hydroxylase Signup and view all the answers

What stimulates the production of cortisol in the adrenal cortex?

Adrenocorticotrophic hormone (ACTH) Signup and view all the answers

Which of the following describes the function of aldosterone?

Increases sodium and water retention Signup and view all the answers

Where are the receptors for ACTH located in cortisol regulation?

Cortical cells of the adrenal cortex Signup and view all the answers

Which hormone is primarily secreted by the adrenal medulla?

Adrenaline Signup and view all the answers

Which hormone primarily increases during fasting and contributes to metabolic effects?

Growth Hormone (GH) Signup and view all the answers

What is the role of Growth Hormone (GH) during moderate exercise?

Stimulates lipolysis Signup and view all the answers

During which conditions does GH play a critical role?

Infection and inflammation Signup and view all the answers

What happens to insulin and IGF-I levels during fasting?

They decrease Signup and view all the answers

What are immediate energy sources for muscle activity?

ATP and Phosphocreatine (PCr) Signup and view all the answers

Which pathway provides glucose in the fastest manner during anaerobic activity?

Glycogenolysis Signup and view all the answers

What effect does Growth Hormone have on muscle mass?

It preserves muscle mass Signup and view all the answers

What triggers the secretion of Growth Hormone Releasing Hormone (GHRH)?

High amino acids and low glucose levels Signup and view all the answers

What is the primary role of gluconeogenesis during fasting?

To maintain blood glucose levels Signup and view all the answers

Which hormone levels decrease significantly during fasting?

Insulin Signup and view all the answers

What substance primarily provides energy for the central nervous system during prolonged fasting?

Ketone bodies Signup and view all the answers

During the transition from fasting to starvation, what metabolic shift occurs?

Increased ketogenesis Signup and view all the answers

Which of the following is a precursor for gluconeogenesis?

Glycerol Signup and view all the answers

What triggers increased glucagon secretion during fasting?

Low blood glucose levels Signup and view all the answers

Which metabolic process occurs in the liver during starvation to provide energy?

Ketogenesis Signup and view all the answers

What happens to protein reserves during prolonged fasting?

They are broken down for gluconeogenesis Signup and view all the answers

What is the primary role of glucagon during prolonged exercise?

Promotes gluconeogenesis Signup and view all the answers

Which hormone decreases in concentration during prolonged exercise?

Insulin Signup and view all the answers

What is the 'Cori cycle' primarily involved in?

Conversion of lactate to glucose Signup and view all the answers

Which energy source is primarily utilized during prolonged exercise?

Fat oxidation Signup and view all the answers

What process does insulin inhibit to regulate energy production?

Lipolysis Signup and view all the answers

What is the fate of lactate produced by type IIb muscle fibers?

It is converted by other muscle fibers to pyruvate Signup and view all the answers

During fasting, which process occurs to provide energy?

Glycogenolysis Signup and view all the answers

What role does cortisol play in the metabolism during exercise?

Stimulates gluconeogenesis Signup and view all the answers

What type of energy production becomes critical when muscle glycogen is depleted during exercise?

Fatty acid oxidation Signup and view all the answers

What effect does Growth Hormone have on muscle tissue?

Stimulates amino acid uptake Signup and view all the answers

Which component is primarily involved in the mobilization of fatty acids during prolonged exercise?

Glucagon Signup and view all the answers

How does Growth Hormone affect glucose metabolism?

Increases gluconeogenesis in the liver Signup and view all the answers

What is one of the primary roles of glucocorticoids?

Increase resistance to stress Signup and view all the answers

Which mechanism is NOT a function of Growth Hormone?

Stimulates fat storage Signup and view all the answers

In terms of metabolic actions, how does Growth Hormone act?

Counteracts insulin Signup and view all the answers

What happens to blood glucose levels in a growing individual under the influence of Growth Hormone?

Blood glucose levels increase Signup and view all the answers

What is a major effect of decreased glucose uptake in adipose tissue due to Growth Hormone?

Increased blood glucose levels Signup and view all the answers

What role does lipolysis play in the effects of Growth Hormone?

Supports blood glucose maintenance Signup and view all the answers

Which effect is associated with glucocorticoids regarding inflammatory responses?

Reduces response to inflammatory stimuli Signup and view all the answers

How does starvation induce hypoglycemia?

Supplies inadequate substrate for gluconeogenesis Signup and view all the answers

Study Notes

Secretion of Steroid Hormones

Steroid hormones are synthesized from cholesterol.
The adrenal cortex is divided into three zones, each producing specific hormones.
The zona glomerulosa produces aldosterone - a mineralocorticoid.
The zona fasciculata and zona reticularis produce cortisol and corticosterone - glucocorticoids.
The adrenal medulla secretes adrenaline and noradrenaline.

Regulation of Glucocorticoids

Glucocorticoids are regulated by the hypothalamic-pituitary-adrenal (HPA) axis.
Corticotrophin-releasing hormone (CRH) from the hypothalamus stimulates the release of adrenocorticotrophic hormone (ACTH) from the anterior pituitary gland.
ACTH binds to melanocortin type 2 receptors (MC2-R) on adrenal cortical cells.
ACTH stimulates the production of cortisol by increasing cholesterol uptake, trafficking, and the expression of key enzymes like P-450ssc and P-450c11.

Effects of Cortisol

Cortisol plays a crucial role in stress response and energy metabolism.
Its actions include increasing glucose output from the liver and promoting catabolism in peripheral tissues like muscle and adipose tissue.
Cortisol is also required for normal vascular reactivity and water excretion.

Growth Hormone and Metabolism

Growth hormone (GH) is a major determinant of growth, promoting cell growth and bone elongation.
GH has metabolic effects that are distinct from its growth-promoting actions, impacting muscle, adipose tissue, and liver.
GH stimulates protein synthesis, decreases protein breakdown, and increases lipolysis.
GH is critical for maintaining muscle mass and helps maintain blood glucose levels during starvation and exercise.

Exercise and Energy

Muscle energy utilization is dependent on the intensity and duration of the exercise.
During moderate exercise, GH stimulates lipolysis to provide alternative energy sources.
During intense exercise, the body relies on stored glycogen, glucose, and fat for energy.
Lactate produced during anaerobic exercise is used by other muscle fibers as an energy source and is also converted back to glucose by the liver.

Eating, Fasting, and Starvation

Ingestion of a meal stimulates the release of insulin, which promotes energy storage in the form of glycogen, protein, and fat.
Insulin inhibits lipolysis by suppressing hormone-sensitive lipase (HSL).
Fasting leads to a decrease in insulin and an increase in glucagon, triggering glycogenolysis, gluconeogenesis, and lipolysis to maintain energy levels.
During prolonged starvation, the body shifts from gluconeogenesis to ketogenesis, utilizing fatty acids as the main energy source.
Ketone bodies are produced in the liver from fatty acids and become an alternative fuel source for the brain and other tissues during prolonged starvation.

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Description

This quiz covers the synthesis, regulation, and effects of steroid hormones, specifically focusing on glucocorticoids like cortisol. It explores the role of the adrenal cortex and the hypothalamic-pituitary-adrenal (HPA) axis in hormone secretion. Test your knowledge on the physiological processes that govern stress responses and hormonal balance.