Endocrinology Quiz on Hormones

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Questions and Answers

Which hormone is a mineralocorticoid produced by the adrenal cortex?

Testosterone

Aldosterone (correct)

Estrogen

Cortisol

What is the primary precursor for all steroid hormones?

Cortisol

Testosterone

Cholesterol (correct)

Insulin

Which class of hormones includes insulin and growth hormone?

Peptides (correct)

Thyroid hormones

Amines

Steroids

What does the adrenal medulla primarily secrete?

Catecholamines Signup and view all the answers

Which hormone is produced only by the gonads?

Testosterone Signup and view all the answers

What is the fate of water-soluble hormones in the bloodstream?

They are found as free form in blood. Signup and view all the answers

Which of the following is a glucocorticoid produced by the adrenal cortex?

Cortisol Signup and view all the answers

Which protein is primarily responsible for binding thyroid hormones in the blood?

Thyroid-binding globulin (TBG) Signup and view all the answers

What hormone primarily stimulates the adrenal medulla to release cortisol?

Adrenocorticotropic Hormone (ACTH) Signup and view all the answers

What is the role of cortisol in the hypothalamic-pituitary-adrenal (HPA) axis?

Inhibiting the synthesis of ACTH Signup and view all the answers

Which of the following is a direct effect of increased cortisol levels in the body?

Increased glycogenolysis in the liver Signup and view all the answers

Where is corticotropin releasing hormone (CRH) synthesized?

Paraventricular region of the hypothalamus Signup and view all the answers

What is one consequence of the negative feedback loop in the HPA axis?

Inhibition of ACTH synthesis Signup and view all the answers

In addition to ACTH, what other hormones are produced from the cleavage of proopiomelanocortin (POMC)?

α-MSN and β-endorphin Signup and view all the answers

What physiological effect does increased lipolysis have in the body during stress?

Increased energy availability from stored fats Signup and view all the answers

Which part of the brain primarily processes inputs to release CRH?

Limbic system Signup and view all the answers

What is the primary mechanism by which T3 exerts its effects in target tissues?

By altering gene expression after binding to nuclear receptors Signup and view all the answers

Which hormone is primarily responsible for stimulating the release of TSH?

Thyrotropin-releasing hormone (TRH) Signup and view all the answers

What effect does TSH have on the thyroid gland?

Promotes the uptake of thyroglobulin into thyroid cells Signup and view all the answers

Which of the following symptoms is associated with hyperthyroidism?

Increased basal metabolic rate (BMR) Signup and view all the answers

Elevated levels of TRH can disrupt which of the following systems?

Reproductive system Signup and view all the answers

What is the condition of goiter primarily related to?

Both hyperthyroid and hypothyroid conditions Signup and view all the answers

What happens to T4 once it enters tissues?

It is converted to T3 by deiodinase Signup and view all the answers

Which of the following statements about the regulation of thyroid hormones is true?

Thyroid hormones exert negative feedback on TSH production Signup and view all the answers

What is the primary hormone responsible for calcium homeostasis in the body?

Parathyroid hormone (PTH) Signup and view all the answers

Which type of bone makes up 80% of total bone mass and is known for its density and strength?

Cortical bone Signup and view all the answers

Which bone cell is responsible for the resorption of bone?

Osteoclasts Signup and view all the answers

What percentage of total body calcium is stored in bones?

99% Signup and view all the answers

Which component forms the organic matrix of bone?

Osteoid Signup and view all the answers

How does the balance between osteoclast and osteoblast activity influence plasma calcium concentrations?

The balance determines calcium release and uptake, influencing plasma levels. Signup and view all the answers

What role does calcitonin play in calcium regulation?

It plays a minor role in regulating plasma calcium levels. Signup and view all the answers

What percentage of bone is composed of hydroxyapatite?

60% Signup and view all the answers

What occurs at the edge of the growth plate during bone development?

Osteoblasts convert cartilage to bone Signup and view all the answers

During which developmental stage does brain growth primarily occur?

Fetal stage Signup and view all the answers

Which nutrient type is essential for normal growth?

Essential fatty acids Signup and view all the answers

What impact does malnutrition during infancy have on growth?

It leads to decreased growth and development Signup and view all the answers

What is the most important hormone for postnatal growth?

Growth hormone Signup and view all the answers

What occurs when growth hormone stimulates the release of IGF-1?

Cell division is stimulated Signup and view all the answers

Which factor can temporarily stunt growth but usually results in a growth spurt upon recovery?

Sickness Signup and view all the answers

Which of the following statements about stress and growth is accurate?

Stress impairs growth Signup and view all the answers

What effect does high levels of cortisol have on DNA synthesis?

Inhibits DNA synthesis Signup and view all the answers

What condition is characterized by excess growth hormone before puberty?

Gigantism Signup and view all the answers

How does growth hormone deficiency affect growth if it occurs before puberty?

Inhibited growth Signup and view all the answers

What is the effect of high levels of growth hormone on the rate of bone maturation?

Accelerated bone maturation Signup and view all the answers

What is the primary result of thyroid deficiency on growth rate?

Very slow growth rate Signup and view all the answers

Which effect is commonly associated with excess growth hormone after the closure of epiphyseal growth plates?

Increase in bone thickness Signup and view all the answers

What impact does cortisol have on protein catabolism?

Stimulates protein catabolism Signup and view all the answers

What clinical condition is associated with a lack of sex steroids?

Tall-eunichoid Signup and view all the answers

Study Notes

Introduction to Endocrine Physiology

Hormones are transported in the blood. Some are bound to proteins, which affects their action.
Hormone receptors have different types, each binding to specific hormones.
The hypothalamic-pituitary axis (HPA) is made up of the hypothalamus, anterior pituitary, and posterior pituitary.
The anterior pituitary releases hormones that regulate other endocrine glands.
Negative feedback regulation controls the release of these anterior pituitary hormones.

Overview of Endocrinology

The endocrine system is a major communication system in the body.
Endocrine glands are not anatomically connected.
Hormone action is specific due to receptors on the target tissues.
Hormone responses vary in speed, from seconds to days.
Hormone concentrations are very low in plasma (10⁻⁹ M to 10⁻¹² M).

Hormones from Previous Lectures

Epinephrine and norepinephrine are related to the autonomic nervous system.
Atrial natriuretic peptide (ANP) is related to the cardiovascular system.
The gastrointestinal system includes hormones like gastrin, secretin, cholecystokinin, and motilin.
Renin-angiotensin, aldosterone, parathyroid hormone, vitamin D, and antidiuretic hormone (ADH) are all components of the renal system.

Chemical Classification of Hormones

Amines—derived from the amino acid tyrosine, including catecholamines (dopamine, norepinephrine, epinephrine, from adrenal medulla).
Steroids—derived from cholesterol, including mineralocorticoids (aldosterone), glucocorticoids (cortisol), and sex steroids.
Peptides—polypeptide chains, such as proopiomelanocortin (POMC) and insulin.

Thyroid Hormone

3,5,3',5'-Tetraiodothyronine (thyroxine, T4) and 3,5,3'-Triiodothyronine (T3) are thyroid hormones.
Cholesterol is the precursor to all steroid hormones.

Steroid Secreting Glands

The adrenal gland (above the kidneys) is divided into cortex and medulla.
Cortex produces mineralocorticoids (aldosterone), glucocorticoids (cortisol), and androgens (DHEA).
Gonads (testes and ovaries) produce sex steroids.
Testes produce testosterone.
Ovaries produce estrogen, progesterone.
Placenta produces estrogen and progesterone.

Peptide Hormones

Proopiomelanocortin (POMC) and insulin are examples.
POMC processes into other hormones (ACTH, endorphins).
Insulin synthesis involves preproinsulin, proinsulin, and insulin.

Hormonal Transport in Blood

Water-soluble hormones (e.g., catecholamines, peptides) travel freely in blood.
Protein-bound hormones (e.g., steroids, thyroid hormone) are bound to transport proteins.

Biotransformation

Hormones are metabolized or deactivated in the liver or kidneys.
Some metabolites are biologically active, while others are inactive.
The transformation of hormones can be activation or inactivation.

Membrane Bound Receptors

Hormone binding to receptors on the plasma membrane activates intracellular signaling pathways.
These pathways can produce rapid effects or alter gene expression.

Intracellular Receptors

Steroid hormones, thyroid hormones, and vitamin D use intracellular receptors.
Hormone binding to receptor activates the receptor as a transcriptional factor.

Integration of Hormone Action

Hormone actions can be complementary (similar effects), antagonistic (opposite effects), or permissive (one hormone needing another).

Control of Hormone Secretion

Hormones can be secreted in pulses or cyclical patterns (e.g., circadian).
Some hormonal releases are regulated by nutrient levels, physical stimuli, or neural control (e.g., autonomic and hypothalamic-pituitary axis).

Anatomy of Hypothalamus and Pituitary

The hypothalamus regulates the release of hormones from the pituitary gland.
The anterior pituitary is connected to the hypothalamus by portal vessels.
The pituitary gland is divided into the anterior and posterior lobes.

Posterior Pituitary

The posterior pituitary consists of axons and nerve endings from hypothalamic neurons.
The posterior pituitary releases antidiuretic hormone (ADH) and oxytocin.

Hypothalamic-Pituitary Axis

Hypophysiotropic hormones from the hypothalamus control the release of anterior pituitary hormones.
Anterior pituitary hormones regulate other endocrine glands (tropic hormones).
Several hypothalamic hormones (CRH, GHRH, TRH, GnRH, DA) control the release of other hormones.

Anterior Pituitary Hormones

Anterior pituitary hormones are secreted from different cell types (e.g., lactotrophs, corticotrophs, thyrotrophs, gonadotrophs, somatotrophs).

Hormonal Feedback Control Systems

Negative feedback loops regulate hormone levels.
Downregulation occurs with excessive stimulation.
Upregulation occurs with insufficient stimulation.

Endocrine Disorders

Primary endocrine disorders affect the gland directly.
Secondary endocrine disorders result from problems regulating the gland.
Hypo-secretion results in decreased hormone levels.
Hyper-secretion results in increased hormone levels.

Introduction to Metabolism

Metabolism studies anabolic and catabolic processes.
Anabolism builds new molecules, while catabolism breaks them down for energy.
Key metabolic organs are liver, skeletal muscle, adipose tissue, and brain.

Carbohydrates, Lipids, and Protein Metabolism

Post-prandial state is after eating and involves glucose, triglyceride, and amino acid usage.
Fasting state involves glycogenolysis and gluconeogenesis.
Proteins are metabolized for fuel and some energy creation pathways (e.g., glycolysis, Krebs cycle)
Lipids, especially fatty acids are metabolized through beta-oxidation.

Absorptive State (Postprandial)

Briefly described as post-meal and involves the metabolic processing of carbohydrates (glucose), protein, and fats to provide energy or store the excess as fat, glycogen, and protein, including some hormone regulation.

Fasting State (Post-absorptive)

Briefly described as the period between meals and involves the use of stored energy (glycogen, fat, and protein) to maintain glucose levels and provide energy, including some hormone regulation.

Glucose-Counterregulatory Systems

Describes the systems acting in opposition to insulin, maintaining blood glucose levels.
Key hormones include glucagon (by liver), epinephrine (by adrenal medulla, effect on liver and muscles), cortisol (by adrenal cortex, effect on lipid, protein, and carbohydrate metabolism), and thyroid hormone.

Sympathetic Control of Plasma Glucose

Sympathetic nervous system directs the body to increase carbohydrate and fat metabolism to provide glucose.
Sympathetic activation increases gluconeogenesis, glycogenolysis, and lipolysis, leading to increased plasma glucose and other metabolic substrates (e.g., fatty acids, glycerol).

Cortisol and Growth Hormone

Cortisol plays a permissive role in gluconeogenesis and lipolysis in the post-absorptive period.
Growth hormone is responsible for stimulating protein synthesis and bone growth.
Their effects can be permissive or active depending on blood levels.

Hypoglycemia and Symptoms

Describes the symptoms and mechanisms associated with low blood glucose (e.g., headache, confusion, dizziness).
Describes the cause of these symptoms, and possible triggers including insulin overdose or drugs.

Thyroid Diseases

Goiter is an enlargement of the thyroid gland, possibly resulting from either hypothyroidism or hyperthyroidism.
Hyperthyroidism causes increased metabolic rate, weight loss despite increased appetite, intolerance to heat, emotional instability and other symptoms.
Hypothyroidism causes decreased metabolic rate, weight gain, intolerance to cold, and other symptoms.

Hypothalamic-Pituitary-Adrenal (HPA) Axis

The HPA axis is responsible for the body's response to stress.
Corticotropin-releasing hormone (CRH from hypothalamus) stimulates the anterior pituitary to release adrenocorticotropic hormone (ACTH).
ACTH stimulates the release of cortisol from the adrenal cortex.
Cortisol's release is regulated by negative feedback (cortisol inhibits the release of CRH and ACTH).

Calcium Homeostasis

Involved mainly in the process of regulating calcium uptake, excretion (with hormone, Vitamin D) and bone health/regrowth, including the major factors regulating blood calcium homeostasis.
The major regulators include parathyroid hormone (PTH), vitamin D, and calcitonin.

Bone Remodeling

Explains the continuous process of bone breakdown and formation.
Osteoclasts break down bone, releasing calcium.
Osteoblasts create new bone, incorporating calcium.

Vitamin D Synthesis and Effects

Vitamin D3 (cholecalciferol) is produced in the skin through UV light and obtained from foods, and is converted to 1,25 dihydroxyvitamin D3.
This active form regulates calcium absorption from the intestines.

Parathyroid Hormone (PTH)

PTH increases blood calcium by acting on the bone, kidneys, and intestines.
PTH stimulates the release of calcium from the bone and the conservation of calcium by the kidneys.
PTH encourages the production of vitamin D to stimulate calcium absorption by the intestines.

Calcitonin

Calcitonin decreases blood calcium by inhibiting bone resorption by osteoclasts.

Growth

Growth hormone (GH) is a key regulator of growth, affecting bones, muscle, and other tissues.
Insulin plays an important role in growth—especially important during the periods of bone and cell growth, especially in adolescents.
Thyroid hormone is necessary for growth and brain development.
Sex hormones (androgens and estrogens) play a crucial role in growth spurts and bone maturation.

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Description

Test your knowledge on various hormones produced by the endocrine system. This quiz covers mineralocorticoids, glucocorticoids, and the role of hormones in the hypothalamic-pituitary-adrenal axis. Perfect for students studying endocrinology or related fields.