Hormones and Endocrine System Overview

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Questions and Answers

What condition is characterized by excessive growth hormone production before the closure of epiphyseal plates?

Acromegaly

Dwarfism

Gigantism (correct)

Hypogonadism

What is a common symptom associated with hyperprolactinemia in men?

Hyperactivity

Height increase

Impotence (correct)

Increased muscle mass

What hormonal function is primarily associated with growth hormone?

Inhibit DNA synthesis

Stimulate amino acid transport (correct)

Inhibit protein synthesis

Decrease lipolysis

What characterizes acromegaly compared to gigantism?

Enlargement of face and extremities after epiphyseal closure Signup and view all the answers

What is a primary symptom of dwarfism resulting from underproduction of growth hormone in infants?

Abnormally short stature Signup and view all the answers

What is a primary function of hormones in the body?

Regulation of metabolism Signup and view all the answers

Which of the following statements about local hormones is true?

They are rapidly destroyed after acting at or near their point of origin Signup and view all the answers

How are hormones classified based on their chemical composition?

Proteins, polypeptides, lipids (steroids), and amino acid derivatives Signup and view all the answers

Which hormones are categorized in Group I based on their mechanism of action?

Steroids and thyroid hormones like T3 and T4 Signup and view all the answers

Which group of hormones is primarily involved in coordinating reproduction?

Sex hormones Signup and view all the answers

What characterizes hormones synthesized by specific tissues?

They are secreted directly into the blood Signup and view all the answers

Which disorder could be linked to a malfunction in hormone functions related to behavior?

Post-traumatic stress disorder (PTSD) Signup and view all the answers

What is a function of hormones in maintaining internal homeostasis?

Controlling blood glucose levels Signup and view all the answers

What is the primary mechanism of action for Group I hormones?

They diffuse through cell membranes and bind to receptors in the cytosol or nucleus. Signup and view all the answers

Which structure is considered an endocrine gland that also functions during pregnancy?

Placenta Signup and view all the answers

What is the role of the second messenger in the action of Group II hormones?

To relay signals within the cell after primary messenger binding Signup and view all the answers

Which hormone is released by the hypothalamus to stimulate the adrenal cortex?

Corticotropin releasing hormone Signup and view all the answers

Which hormone is released by the anterior pituitary gland and stimulates the secretion of thyroid hormones?

Thyroid stimulating hormone Signup and view all the answers

Which of the following glands is NOT classified as part of the endocrine system?

Kidneys Signup and view all the answers

What changes occur in the hormone-receptor complex of Group I hormones upon activation?

It changes in size, conformation, and surface charges. Signup and view all the answers

What functions does the hypothalamus primarily control?

Release of hormones from the pituitary gland Signup and view all the answers

What is the primary role of prolactin in lactation?

It induces growth of the mammary gland and stimulates lactogenesis. Signup and view all the answers

Which substance serves as the major inhibiting factor for prolactin secretion?

Dopamine Signup and view all the answers

Which group does prolactin belong to in the classification of anterior pituitary hormones?

Protein hormones Signup and view all the answers

Which of the following conditions is commonly associated with excessive secretion of prolactin?

Hyperprolactinemia Signup and view all the answers

Which anterior pituitary hormone is primarily responsible for regulating the function of other endocrine glands?

Thyroid-stimulating hormone Signup and view all the answers

What is the common manifestation of hyperprolactinemia in women?

Amenorrhea and galactorrhea Signup and view all the answers

What physical changes does prolactin induce in the mammary gland?

Promotes hypertrophy and prepares for lactation. Signup and view all the answers

Which hormone secretion is inhibited by excessive levels of TSH, T3, and T4?

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

Study Notes

Hormones

Organic compounds produced by the endocrine system, secreted directly into the bloodstream.
Act near their release site or at a distant organ.

Endocrine System

A group of glands that regulate and control functions by producing and secreting hormones.
Glands release hormones directly into the bloodstream.

General Functions of Hormones

Regulate metabolism of carbohydrates, proteins, lipids, and minerals.
Support cell growth.
Maintain internal homeostasis.
Impact behavior, including fear, depression, and sexual behavior.
Coordinate reproduction.
Facilitate responses to external stimuli.

Characters of Hormones

Synthesized by specific tissues (glands).
Secreted directly into the blood.
Carried by the blood to their site of action.

Local Hormones

Physiologically active substances released from specific tissue sites.
Act at or near their point of origin.
Rapidly destroyed before dispersal.
Includes: acetylcholine, histamine, serotonin, prostaglandins, prostacyclin, thromboxanes, and plasma polypeptides like angiotensin and plasma kinins.

Classification of Hormones (Chemical Composition)

Proteins: insulin, growth hormone (GH), thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), parathyroid hormone, and prolactin.
Polypeptides: pituitary hormones - oxytocin, antidiuretic hormone (ADH), and adrenocorticotropic hormone (ACTH).
Lipids (steroids): sex hormones - estrogen, progesterone, and androgens.
Amino acid derivatives: thyroid hormone (T3 & T4), epinephrine, norepinephrine, and serotonin.

Classification of Hormones (Mechanism of Action)

Group I: Hormones that bind to intracellular receptors (steroids, T3, T4, and calcitriol).
- Diffuse through the cell membrane and bind to specific receptors in the cytosol or nucleus, forming hormone-receptor complexes.
- The complex undergoes activation, leading to changes in size, conformation, and surface charges.
- This activated complex binds to DNA at specific hormone response elements (HREs), potentially activating or inactivating metabolic processes.
Group II: Hormones that bind to cell surface receptors.
- The hormone (first messenger) binds to a specific cell membrane receptor, activating a second messenger within the cytosol.

Endocrine Glands

Major glands include the hypothalamus, pituitary, thyroid, parathyroid, islets of the pancreas, adrenal glands, testes (males), and ovaries (females).
The placenta also functions as an endocrine gland during pregnancy.
Other organs secrete hormones or hormone-like substances, including:
- Kidneys (renin, angiotensin, erythropoietin).
- Digestive system (gastrin, secretin, cholecystokinin).

Hypothalamus

Part of the central nervous system located at the base of the brain.
Releases hormones that control the release of hormones from the pituitary gland.
Secretes releasing hormones that regulate the secretion of anterior pituitary hormones.

Pituitary Gland

Located at the base of the brain.
Referred to as the 'master gland' due to its influence on many body organs.
Composed of two lobes: anterior and posterior.
The anterior pituitary regulates and controls most other endocrine glands.

Anterior Pituitary Hormones

Three Groups:
- Protein Hormones: prolactin (PRL) and GH.
- Glycoprotein Hormones: TSH, LH, FSH.
- Pro-opio-melano-cortin (POMC) Peptide Hormones: ACTH, melanocyte-stimulating hormone (MSH), β-lipotropin (β-LPH), endorphin, and enkephalin.

Prolactin (PRL)

A protein hormone with 194-199 amino acids.
Initiates and maintains lactation in conjunction with estrogens and progesterone.
Promotes mammary gland growth.
Stimulates milk production after childbirth (lactogenesis).

Control of Prolactin Secretion

The hypothalamus suppresses prolactin secretion by the pituitary gland.
Dopamine acts as the primary prolactin-inhibiting factor.

Disease States of Prolactin (Hyperprolactinemia)

Excessive prolactin secretion.
Causes include prolactin-secreting tumors and certain medications (anti-dopaminergic drugs).
Common manifestations in women include amenorrhea (lack of menstrual cycles) and galactorrhea (excessive milk secretion).
In men, hyperprolactinemia often leads to hypogonadism (decreased sex drive, sperm production, and impotence), and occasionally gynecomastia (breast enlargement).

Growth Hormone (GH, Somatotropin)

A protein consisting of 191 amino acids.
Anabolic hormone that increases amino acid transport into muscle cells, promoting protein, DNA, and RNA synthesis.
Stimulates lipolysis, free fatty acid and glycerol release from adipose tissues, and ketogenesis in the liver.
Increases mineral absorption (calcium, magnesium, phosphate) and their incorporation into the skeleton.
Possesses prolactin-like effects, binding to lactogenic receptors and stimulating mammary glands and milk production.

Disorders of GH

Gigantism and Acromegaly (Overproduction of GH)
- Gigantism: Accelerated growth of long bones due to excessive GH production before epiphyseal plate closure.
- Acromegaly: Enlargement of extremities, face, and jaw due to excessive GH production after epiphyseal plate closure and long bone growth cessation.
Dwarfism (Underproduction of GH)
- GH deficiency in infants leads to growth failure.
- Characterized by abnormally short stature compared to peers, especially in adults.

Regulation of Hypothalamic Hormones

Secretion is controlled by higher brain centers, anterior pituitary hormones, and feedback regulation from target hormones.
- For example, TRH (thyrotropin-releasing hormone) secretion is inhibited by excess TSH, T3, and T4.

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Description

Explore the fascinating world of hormones and the endocrine system through this quiz. Learn about the functions, characteristics, and types of hormones, including local hormones. Test your understanding of how these organic compounds regulate various physiological processes.