Endocrine Glands and Thyroid Gland Overview

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Questions and Answers

What effect does elevated T3 concentration have on TRH and TSH secretion?

Increases both TRH and TSH secretion

Decreases both TRH and TSH secretion (correct)

Increases TRH and decreases TSH secretion

Decreases TRH and increases TSH secretion

Which condition is characterized by decreased levels of thyroid hormones (TH)?

Hyperthyroidism

Graves' Disease

Hypothyroidism (correct)

Hashimoto’s Disease

What is the primary cause of Hashimoto’s Disease?

Excessive iodine intake

Genetic predisposition

Pituitary gland malfunction

Autoimmune dysfunction targeting the thyroid (correct)

Which disease is the most common cause of hyperthyroidism?

Graves' Disease (D) Signup and view all the answers

What is the treatment for hypothyroidism as mentioned?

Administration of synthetic TH (B) Signup and view all the answers

What effect does elevated levels of TH have on the metabolic rate?

It heightens the metabolic rate (A) Signup and view all the answers

Which hormone is released by the anterior pituitary that is inhibited by elevated T3 levels?

Thyroid stimulating hormone (TSH) (A) Signup and view all the answers

Which of the following is NOT a potential cause of hyperthyroidism?

Decreased TH release from the thyroid gland (A) Signup and view all the answers

What hormonal levels are typically low in patients with Graves' disease?

TRH and TSH (C) Signup and view all the answers

What is a hallmark characteristic of Graves' disease?

Protrusion of the eyes (A) Signup and view all the answers

What type of hormones does the adrenal cortex produce?

Hydrophobic hormones (C) Signup and view all the answers

Which part of the adrenal glands is primarily responsible for short-term stress responses?

Adrenal medulla (B) Signup and view all the answers

Cortisol is part of which type of stress response?

Long-term stress response (A) Signup and view all the answers

What physiological effects does cortisol have when levels are high in the morning?

Mobilization of nutrients (C) Signup and view all the answers

What is one of the effects of sustained cortisol release due to chronic stress?

Suppression of immune function (A) Signup and view all the answers

What triggers the daily release of cortisol as morning approaches?

Decline in melatonin levels (C) Signup and view all the answers

What is the primary role of the thyroid hormone (TH)?

Regulates metabolic rate and production of heat (D) Signup and view all the answers

Which of the following hormones produced by the thyroid gland is responsible for regulating calcium levels in the blood?

Calcitonin (A) Signup and view all the answers

Why is iodine essential for the production of thyroid hormones?

It is a critical component of the hormone structure (C) Signup and view all the answers

What mechanism controls the secretion of thyroid hormone?

Negative feedback mechanism (D) Signup and view all the answers

Which of the following glands produces TRH and TSH, which are important in regulating TH release?

Hypothalamus (A) Signup and view all the answers

How do T3 and T4 exit the bloodstream to enter target cells?

Through specific receptors on cell membranes (C) Signup and view all the answers

Which physiological role is performed by thyroid hormones T3 and T4 upon entering target cells?

Turn on specific genes through receptor binding (D) Signup and view all the answers

What shape is the thyroid gland described as?

Butterfly (C) Signup and view all the answers

What is the primary role of epinephrine during the fight or flight response?

To increase heart rate and respiratory rate (C) Signup and view all the answers

How does glucagon affect blood glucose levels?

It increases blood glucose by converting glycogen to glucose. (B) Signup and view all the answers

Which of the following is a characteristic of Type I Diabetes?

It typically occurs before the age of 25. (B) Signup and view all the answers

What is the primary effect of insulin in the body?

It helps cells absorb glucose. (B) Signup and view all the answers

What syndrome is characterized by high glucose levels in the blood?

Diabetes Mellitus (B) Signup and view all the answers

In individuals with Type II Diabetes, what is primarily responsible for the condition?

Insulin resistance in body tissues (A) Signup and view all the answers

What hormone has opposing effects to glucagon?

Insulin (B) Signup and view all the answers

Which of the following symptoms is associated with Type I diabetes?

Extreme thirst and hunger (B) Signup and view all the answers

Which of the following is a symptom of Type II diabetes?

Frequent urination (C) Signup and view all the answers

What is the role of luteinizing hormone (LH) in the body?

Stimulates testosterone production (C) Signup and view all the answers

Which complication is associated with poorly managed diabetes?

Kidney dysfunction (A) Signup and view all the answers

What does testosterone primarily influence in males?

Sperm production (D) Signup and view all the answers

Which hormone is primarily responsible for regulating the menstrual cycle?

Estrogen (D) Signup and view all the answers

Which of the following is a function of estrogen?

Thickening the endometrial lining (A) Signup and view all the answers

What long-term risk is associated with chronic high levels of glucose in blood due to diabetes?

Development of heart disease (B) Signup and view all the answers

What hormone is released by the pituitary gland in response to GnRH?

Luteinizing hormone (A) Signup and view all the answers

Study Notes

Endocrine Glands and Tissues

The endocrine system includes several glands and tissues
These are the pineal gland, pituitary gland (anterior and posterior), thyroid gland, adrenal glands, pancreas, and gonads (testes and ovaries)

Thyroid Gland

Butterfly-shaped, located in front of the trachea, below the larynx
Releases two hormones:
- Thyroid hormone (TH): regulates metabolic rate and heat production. Most body cells are target cells. It increases energy use, glucose and lipid use, and promotes cellular ATP production and protein synthesis.
- Calcitonin: regulates calcium levels in the blood.

Thyroid Hormone (TH)

Two forms: T3 and T4
Differ in the number of iodine atoms (3 vs 4)
T3 and T4 are hydrophobic and bound to blood proteins
Released T3/T4 enters bloodstream and cells; T3 binds to intracellular receptors, triggering a nuclear response, for example, affecting gene expression
Iodine from the diet is necessary to produce T3 and T4
Salt is often iodized
Hypothalamus ultimately controls TH release; use of negative feedback
TH levels are maintained by a negative feedback loop
Checking TRH, TSH, and TH levels is important when metabolic imbalances are suspected

Regulation of TH Secretion

TRH (thyrotropin-releasing hormone) from the hypothalamus and TSH (thyroid-stimulating hormone) from the anterior pituitary regulate TH secretion
Elevated T3 in the blood inhibits the release of both TRH and TSH

Thyroid Disorders

Hypothyroidism: Reduced levels of TH, leading to a slower metabolism
Causes can include problems with the hypothalamus, anterior pituitary, or thyroid gland
Symptoms include fatigue, memory impairment, depression, swollen face, weight gain, dry skin, muscle cramps, shaggy hair, and hair loss.
Could be due to Hashimoto's disease where the immune system attacks the thyroid
Hypothyroidism is treatable
Hyperthyroidism: Elevated levels of TH, leading to a faster metabolism
Causes can include problems with the hypothalamus, anterior pituitary, or thyroid gland
Symptoms include nervousness, irritability, insomnia, depression, weight loss, strong hunger, diarrhea, fragile fingernails, shaking hands, warm moist skin, increased body temperature.
Could be Graves' Disease where antibodies mimic TSH and stimulate the thyroid inappropriately

4. Adrenal Glands

Small glands located on top of each kidney
Two regions:
- Adrenal cortex: produces 20 steroid hormones (hydrophobic), including male and female sex hormones, cortisol
- Adrenal medulla: produces short-term stress hormones (e.g., epinephrine, norepinephrine)

Stress Responses

Enables the body to adapt by mobilizing nutrients, increasing metabolic rates, increasing nutrient and oxygen delivery, and suppressing non-essential functions
Short-term stress (e.g., exercise, excitement) stimulates the "fight or flight" response, increasing heart rate, breathing, oxygen, glucose supply, skeletal muscle readiness, and blood pressure and suppressing non-essential organs.
Long-term stress causes the hypothalamus to release hormone CRH which causes the anterior pituitary to stimulate the adrenal cortex, resulting in mineralcorticoid and glucocorticoid production.

Cortisol

Released daily, part of the circadian rhythm
Involved in long-term stress responses
Mobilizes stored nutrients (carbs, fats, proteins) for energy
Suppresses immune system function

5. Pancreas

Located on the back of the stomach
Produces two antagonistic hormones:
- Glucagon: increases blood glucose levels by stimulating glycogen breakdown in the liver and releasing glucose into the bloodstream
- Insulin: decreases blood glucose levels by inhibiting glycogen breakdown in the liver, stimulating muscle and adipose tissue uptake

Diabetes Mellitus

High blood glucose levels
Type I - Early onset; autoimmune condition where the body destroys insulin-producing cells in the pancreas, requiring insulin injections.
Type II - Later onset; body becomes insensitive to insulin, often related to diet, lifestyle, and obesity
Symptoms include- Extreme thirst and hunger; frequent urination; unexplained weight loss; fatigue, blurred vision, nausea and vomiting
Untreated diabetes can lead to long-term complications like kidney disease, nerve damage, cardiovascular issues and blindness

6. Gonads (Testes and Ovaries)

Testes (males) and ovaries (females)
Produce gametes and sex hormones
HPG Axis: Hypothalamus, pituitary gland and Gonads are stimulated by Gonadotrophin releasing hormone from the hypothalamus; Anterior pituitary releasing LH and FSH which stimulate the gonads.

Testosterone

Produced in the testes
Important for sperm production
Promotes male secondary sex characteristics; development of male genitals; maintenance of male reproductive structures ; sexual drive.

Estrogen

Found in both males and females but higher in females (ovaries)
Important for menstrual cycle
Development and maintenance of female reproductive structures
Development of secondary sexual characteristics, maintaining bone density, and prepares for pregnancy

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Description

This quiz covers the key concepts of the endocrine system, focusing primarily on the endocrine glands and specifically the thyroid gland. It discusses the role of thyroid hormones, their functions in the body, and the importance of iodine in hormone production. Test your knowledge of how these glands impact metabolism and overall health.