Endocrinology Quiz: Hormones and Their Functions

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Questions and Answers

What is the primary function of growth hormone-releasing hormone (GHRH)?

Stimulates secretion of thyroid-stimulating hormone

Inhibits secretion of prolactin

Inhibits growth hormone secretion

Stimulates secretion of growth hormone (correct)

Which hypothalamic hormone is responsible for inhibiting prolactin secretion?

Prolactin-inhibiting hormone (PIH) (correct)

Corticotropin-releasing hormone (CRH)

Gonadotropin-releasing hormone (GnRH)

Somatostatin

What role do stressors have in hormone regulation according to the feedback control mechanisms?

Inhibit thyroid-stimulating hormone secretion

Enhance growth hormone secretion

Increase CRH production (correct)

Decrease CRH production

Which of the following hypothalamic hormones has a structure of 3 amino acids and stimulates the secretion of thyroid-stimulating hormone?

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

What is the outcome of negative feedback inhibition in the hypothalamic-pituitary axis?

Regulation of target tissue hormone levels Signup and view all the answers

Which hormone is produced by the supraoptic nucleus of the hypothalamus?

Oxytocin Signup and view all the answers

What triggers the release of antidiuretic hormone (ADH)?

Increase in blood osmolality Signup and view all the answers

Which of the following hormones is classified as a releasing hormone?

Gonadotropin-releasing hormone Signup and view all the answers

The anterior pituitary is primarily controlled by which of the following mechanisms?

Releasing and inhibiting hormones via the hypothalamo-hypophyseal portal system Signup and view all the answers

Which hormone acts as a trophic hormone that stimulates hormone secretion in other glands?

Growth hormone Signup and view all the answers

What is the primary effect of glucocorticoids during stressful situations?

Regulate glucose release from the liver Signup and view all the answers

What condition is characterized by chronic high levels of glucocorticoids?

Cushing's Syndrome Signup and view all the answers

Which stage of the General Adaptation Syndrome (GAS) is characterized by major physiological adjustments to stress?

Stage of resistance Signup and view all the answers

What physiological changes can occur due to chronic stress and increased cortisol levels?

Increase in fat redistribution and potential depression Signup and view all the answers

Which of the following is NOT a purpose of exogenous glucocorticoids?

Inhibit glucose metabolism Signup and view all the answers

The activation of the adrenal glands during stress is part of which stage of GAS?

Alarm reaction Signup and view all the answers

What physical manifestation is commonly associated with Cushing's syndrome?

Buffalo hump and moon face Signup and view all the answers

What is the primary component required for the synthesis of thyroxine and triiodothyronine?

Thyroglobulin Signup and view all the answers

How does the thyroid gland respond when stimulated by TSH?

Thyroid hormones dissociate from thyroglobulin. Signup and view all the answers

Which molecules are formed by the attachment of iodines to tyrosines in thyroglobulin?

Monoiodotyrosine (MIT) and diiodotyrosine (DIT) Signup and view all the answers

What is a role of thyroid hormones in the body?

Elevates basal metabolic rate Signup and view all the answers

What fluid fills the interior of the thyroid follicles?

Colloid Signup and view all the answers

What happens to T4 inside target cells?

It is converted to T3. Signup and view all the answers

What role do receptor proteins play in the action of thyroid hormones?

They bind to DNA and allow for gene expression changes. Signup and view all the answers

What is the outcome of the binding of T3 to the hormone response element on DNA?

Corepressor proteins are removed. Signup and view all the answers

Study Notes

Endocrine Glands

Endocrine glands are ductless glands, secreting hormones directly into the bloodstream.
Hormones act on target cells with specific receptors.
Many organs secrete hormones besides those discussed in Endocrine system (e.g., heart, liver, kidneys, adipose tissue).

Learning Objectives - Endocrine System

Identify glands involved in endocrine function.
Understand hormone types.
Learn about hormone regulation and control mechanisms.
Examine hormone structures and synthesis.
Study permissiveness and synthesis mechanisms.
Explore diseases from over or under hormone production.

Endocrine vs Exocrine Glands

Endocrine glands secrete hormones directly into the blood.
Exocrine glands secrete products into ducts, often to body surface or internal lumens.

Inputs That Act Directly on Endocrine Gland Cells

Ions or nutrients
Neurotransmitters
Hormones

General Info on Endocrine Glands

Endocrine glands are ductless and secrete hormones into the bloodstream.
Hormones are transported to target cells with specific receptors.
Hormones help regulate metabolism, growth, and reproduction.

Classification of Hormones by Action

Polar Hormones (water-soluble): Cannot pass through plasma membranes; must be injected. Examples include polypeptides, glycoproteins, catecholamines (epinephrine, norepinephrine).
Nonpolar Hormones (lipid-soluble): Can enter target cells directly; can be taken orally. Examples include steroids, thyroid hormone, and melatonin.

Chemical Classification of Hormones

Amines: Derived from tyrosine and tryptophan. Examples include hormones from adrenal medulla, thyroid, and pineal glands.
Polypeptides and Proteins: Examples include antidiuretic hormone (ADH), insulin, and growth hormone.
Glycoproteins: Long polypeptides bound to a carbohydrate. Examples include follicle-stimulating hormone (FSH), luteinizing hormone (LH), and erythropoietin (EPO).
Steroids: Lipids derived from cholesterol. Examples include testosterone, estradiol, progesterone, cortisol, and aldosterone.

Polypeptide and Glycoprotein Hormones - Examples

Hormone	Structure	Gland	Primary Effects
ADH	9 amino acids	Posterior pituitary	Water retention and vasoconstriction
Oxytocin	9 amino acids	Posterior pituitary	Uterine and mammary contractions
Insulin	21 and 30 amino acids (double chain)	Beta cells in islets	Cellular glucose uptake, lipogenesis, and glycogenesis
Glucagon	29 amino acids	Alpha cells in islets	Hydrolysis of stored glycogen and fat
ACTH	39 amino acids	Anterior pituitary	Stimulation of adrenal cortex
Parathyroid hormone	84 amino acids	Parathyroid	Increase in blood Ca2+ concentration
FSH, LH, TSH	Glycoproteins	Anterior pituitary	Stimulation of growth, development, and secretory activity of target glands
Epo	Glycoprotein	Kidneys	Regulates maturation of red blood cells

Hormone Interactions

Synergistic Effects: Two hormones working together to amplify the effect (1 + 1 > 2).
Permissive Effects: One hormone enhancing the effect of another hormone.
Antagonistic Effects: Two hormones having opposing effects.

Hormone Synthesis and Secretion

Peptide hormones are synthesized in the rough endoplasmic reticulum and processed in the Golgi apparatus.
Steroid hormones are derived from cholesterol.

Hormone Pathways

Hypothalamus regulates the anterior pituitary via releasing and inhibiting hormones.
A hypophysiotropic hormone is the first in a three-hormone sequence. It regulates the secretion of an anterior pituitary hormone, which in turn may regulate the secretion of another hormone from another gland.

Hypothalamus and Pituitary Gland

The hypothalamus is essential for homeostasis and autonomic system regulation.
It contains centers for hunger/satiety, thirst, body temperature regulation, sleep, arousal, emotions, and the control of the endocrine system.
It controls pituitary gland hormone secretion.
Hypothalamic hormones (releasing and inhibiting) regulate the anterior pituitary gland.

Posterior Pituitary Hormones

Stores and releases ADH (antidiuretic hormone)
Stores and releases oxytocin.

Feedback Control of the Anterior Pituitary

The final product of the hormone pathway negatively regulates secretion.
The relationship between the hypothalamus, pituitary, and target tissue is called an "axis".
Inhibition can occur at pituitary or hypothalamus level.

Higher Brain Controls

The hypothalamus receives input from the brain regions, influencing hormone secretion.
Stressors increase CRH production.
Circadian rhythms affect hormone secretion.

Thyroid Gland

Located below the larynx, with two lobes connected by isthmus.
Consists of follicles filled with colloid, containing thyroglobulin. Follicular cells produce thyroxine (T4) and triiodothyronine (T3). Parafollicular cells secrete calcitonin.
Iodine is crucial for thyroid hormone production.
Thyroid hormone regulation is controlled by TRH and TSH.
Thyroid hormone functions include metabolic rate, heat production, growth, and development.
Iodine deficiency can lead to hypothyroidism and goiter.
Grave's disease causes excessive thyroid hormone production.

Adrenal Gland

Atop the kidneys, with cortex and medulla responsible for different hormones.
Adrenal medulla (neural tissue): secretes epinephrine and norepinephrine (fight or flight).
Adrenal Cortex (glandular epithelium): secretes corticosteroids (mineralocorticoids, glucocorticoids, adrenal androgens).

Adrenal Cortex - Hormones

Mineralocorticoids (aldosterone): regulate sodium (Na+) and potassium (K+) balance.
Glucocorticoids (cortisol): regulate glucose metabolism.
Adrenal androgens (weak sex hormones): supplement those produced by gonads.

Cortisol Actions

Stimulates protein degradation.
Stimulates gluconeogenesis and inhibits glucose utilization.
Stimulates lipolysis.

Adrenal Insufficiency

The general term for any condition where cortisol levels are chronically below normal.
Symptoms include weakness, fatigue, and loss of appetite.

Cushing's Syndrome

Result of chronically high cortisol levels, even in non-stressed situations.
Causes include primary adrenal defects or secondary pituitary defects.
Symptoms include osteoporosis, muscle weakness, thin easily-bruised skin, high blood sugar, immunosuppression, redistribution of fat, and hypertension.

Actions of the Sympathetic Nervous System, Including Epinephrine from the Adrenal Medulla

Increased hepatic and muscle glycogenolysis.
Increased breakdown of adipose tissue.
Increased cardiac function.
Diversion of blood from viscera to skeletal muscle tissue.
Increased lung ventilation.

Endocrine Control of Growth

The endocrine system regulates growth.
Factors include multiple hormones (e.g., growth hormone, IGF-1 and IGF-2, thyroid hormone, insulin, sex hormones, and cortisol).
Growth occurs through cell division and protein synthesis, primarily in skeletal growth.
Environmental factors (nutrition) and genetics are also influential.

Pancreas (Endocrine Function)

The pancreas has endocrine cells in islets of Langerhans (alpha and beta).
Alpha cells secrete glucagon (raises blood glucose).
Beta cells secrete insulin (lowers blood glucose).

Diabetes Mellitus

Characterized by fasting hyperglycemia (and glucose in urine).
Type 1: Beta cell destruction = lack of insulin secretion.
Type 2: Insulin resistance (decreased tissue sensitivity).
Gestational: Insulin secretion inadequate during pregnancy.

Types of Endocrine Disorders

Hyposecretion: Secretion of too little hormone.
Hypersecretion: Secretion of too much hormone.
Hyporesponsiveness: Decreased responsiveness of target cells.
Hyperresponsiveness: Increased responsiveness of target cells.

Hormone Transport

Most peptide and catecholamine hormones are water-soluble and transported dissolved in the plasma.
Steroid and thyroid hormones are poorly soluble and transported bound to plasma proteins. Only the free hormones interact with target cells.

Regulation of Responsiveness of Hormones

Ability of a cell to respond is dependent on the presence of specific receptors.
Up-regulation: Increased number of receptors.
Down-regulation: Decreased number of receptors.
Permissiveness: One hormone must be present for another hormone to exert its full effect.

Effects of Hormone-Receptor Binding

Peptide and Catecholamine (Amine) Hormones: Bind to receptors on cell membranes. Mechanisms can include affecting enzyme activity or activating G proteins.
Steroid and Thyroid Hormones: Bind to intracellular receptors inside the cell (nuclear or cytoplasmic). Mechanisms often involve transcription of specific genes.

Pharmacological Effects of Hormones

Very high concentrations of hormones administered for medical purposes might produce different effects compared to physiological levels.
These abnormal hormone levels can also occur in diseases with excessive hormone secretion.

Hormones that Control Other Hormones

Tropic hormones control another endocrine gland's hormone secretion.
Trophic hormones control hormone secretion and stimulate gland growth.

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Description

Test your knowledge on key hormones, their regulation, and physiological roles in the human body. This quiz covers various aspects of the hypothalamic-pituitary axis, growth hormone functions, and the impact of stress on hormone levels. Perfect for students studying endocrinology or related fields.