Endocrinology Lecture Review

These flashcards cover major historical events in endocrinology, hormone classification, receptor characteristics, signaling pathways (AC-cAMP, RTK, GPCR-PLC, JAK-STAT), classical and modern research methodologies, and the anatomy and hormones of the pituitary gland.

What historical figures demonstrated that removing the pancreas causes diabetes?

Von Mering and Minkowski

Who discovered and isolated insulin from islet cells, demonstrating its effectiveness in curing diabetes?

Banting and Best

Which specific cells within the pancreas produce insulin?

Beta cells of the islets of Langerhans

Which specific cells within the pancreas produce glucagon?

Alpha cells of the islets of Langerhans

Who conducted the famous experiment using frog vagal nerves to show that nerves release secreted factors affecting heart rate?

Otto Loewi

What enzyme, identified by Sutherland, acts as a major transducer of hormonal effects by converting ATP to cAMP?

Adenylate cyclase

Which hormone, released by the thyroid's C-cells, is involved in decreasing blood calcium levels?

Calcitonin

Which hormone, also known as ADH, is released from the posterior pituitary in response to dehydration to increase fluid reabsorption and blood pressure?

Vasopressin

What is a key difference in the speed and duration of action between nervous and endocrine signaling?

Nervous: fast, short half-life; Endocrine: slow, long half-life

What amino acid is the primary precursor for amine hormones such as epinephrine and dopamine?

Tyrosine

What amino acid is the precursor for melatonin?

Tryptophan

Peptides and larger proteins are classes of hormones that typically bind to what type of receptors?

Membrane-bound receptors

What unique structural feature characterizes glycoprotein hormones like TSH and FSH?

Attached carbohydrate units

What class of lipid-derived hormones (from arachidonic acid) primarily acts locally and uses membrane-bound receptors?

Eicosanoids, e.g., Prostaglandins

What common precursor molecule is used in the biosynthesis of all steroid hormones?

Cholesterol

Where are steroid hormones primarily metabolized?

In the liver

How is thyroxine stored and transported due to its hydrophobic nature, despite being tyrosine-derived?

Protected by plasma membranes, deiodinated for metabolism

What method of hormone delivery describes a cell stimulating itself via secreted factors?

Autocrine

What method of hormone delivery involves hormones traveling locally through interstitial fluids to adjacent cells?

Paracrine

What is the fundamental mechanism of action for all peptide hormones and neurotransmitters at the cellular level?

They act on membrane receptors

What is the fundamental mechanism of action for all steroid hormones and thyroxine at the cellular level?

They act on intracellular receptors to control gene expression

What characteristic describes a hormone-receptor interaction where a precise fit ensures binding to its intended target?

High specificity

What does it mean for hormone binding to be 'saturable'?

There is a finite number of receptors, so increasing hormone eventually has no additional binding

At what hormone concentration, relative to the Kd, are 50% of the receptors typically occupied?

When [H] equals Kd

In a competitive binding assay, what is mixed with receptors and a fixed amount of radiolabeled hormone to determine specific binding?

Increasing concentrations of unlabeled hormone

What information can be obtained from the y-intercept of a Scatchard plot?

Bmax, the total number of binding sites/receptors

What enzyme in the AC-cAMP pathway converts ATP into cAMP?

Adenylate cyclase

What enzyme is activated by cAMP, leading to the phosphorylation of target proteins?

Protein Kinase A (PKA)

What is CREB, and what is its function in the AC-cAMP pathway?

A transcription factor that is phosphorylated by PKA and binds to CRE to turn on genes

What class of drugs, which includes caffeine, inhibits phosphodiesterase and thus increases cellular cAMP levels?

Methylxanthines

According to Sutherland's criteria, what is expected of exogenous cAMP if a hormone signals via the AC-cAMP pathway?

It should mimic the hormone's effect

What enzyme initiates GPCR inactivation by binding to and phosphorylating the receptor tail?

GRK2 (GPCR Kinase 2)

What molecule binds to phosphorylated GPCRs, blocking G protein binding and facilitating receptor internalization?

Beta-arrestin (Barrestin)

What enzyme acts to decrease cAMP levels during GPCR inactivation?

PDE4 (phosphodiesterase 4)

What is the initial key event for receptor tyrosine kinases (RTKs) after ligand binding?

Receptor dimerization and autophosphorylation

In RTK signaling, what amino acid residues are typically phosphorylated during autophosphorylation?

Tyrosine residues

What enzyme generates PIP3 from PIP2 in the RTK pathway, especially for insulin signaling?

PI3K (Phosphoinositide 3-kinase)

What kinase is activated by PIP3 in the RTK pathway, leading to many downstream physiological effects?

PKB (Protein Kinase B / Akt)

In the GPCR-PLC (calmodulin) pathway, what G protein alpha subunit activates Phospholipase C (PLC)?

Gq-alpha

What two second messengers are produced when PLC hydrolyzes PIP2?

IP3 and DAG

Which of the second messengers from PLC is responsible for increasing intracellular calcium levels?

IP3

What calcium-binding protein is activated by increased intracellular Ca2+ and then activates effector proteins?

Calmodulin

In the JAK-STAT pathway, what enzymes are activated by receptor dimerization and then autophosphorylate?

JAK kinases

What transcription factors bind to phosphorylated receptors in the JAK-STAT pathway and are then phosphorylated by JAK?

STAT proteins

Where do phosphorylated STAT proteins translocate to elicit their final effect?

To the nucleus to activate gene expression

What classical methodology involves the surgical removal of an endocrine gland to study its function, often leading to compensatory hypertrophy?

Loss of function bioassay

What is the scientific purpose of hormone purification?

To determine if a substance is the active hormone

What immunological technique uses a radiolabeled hormone to compete with an unknown amount of unlabeled hormone for antibody binding sites?

Radioimmunoassay (RIA)

What immunological technique uses an enzyme-linked antibody to produce a colored product, quantifying hormones or antigens in fluid samples?

ELISA (Enzyme-linked immunosorbent assay)

What histological dye stains DNA and other acidic components blue?

Hematoxylin

What histological dye stains cytoplasm and basic components pink?

Eosin

What technique uses a labeled complementary RNA probe to visualize where specific genes are expressed within cells or tissues?

In-situ hybridization

What general approach in genetics involves manipulating a specific gene (e.g., knockout) to determine its function?

Reverse genetics

What technology allows for the mass production of human hormones like insulin by inserting their genes into bacteria?

Recombinant DNA technology

What molecular technique converts mRNA into cDNA and then amplifies specific target sequences to determine gene expression?

RT-PCR (Reverse Transcriptase Polymerase Chain Reaction)

What molecular technique provides a comprehensive view of all genes expressed in a sample but lacks spatial information?

RNA-seq (RNA sequencing)

From which embryonic germ layer is the anterior pituitary (pars distalis/tuberalis) derived?

Oral ectoderm

What anterior pituitary hormone is crucial for mammary gland development and milk production?

Prolactin (PRL)

What hypothalamic substance acts as the primary inhibitory factor for prolactin release?

Dopamine

What is the hypothalamic releasing hormone that promotes the secretion of Growth Hormone?

GHRH (Growth Hormone Releasing Hormone / Somatocrinin)

What hypothalamic hormone inhibits the release of Growth Hormone?

Somatostatin (SST)

What condition arises from a deficiency of Growth Hormone during childhood, leading to stunted but proportional growth?

Pituitary dwarfism

What condition results from the overproduction of Growth Hormone during adulthood, causing disproportionate bone growth in extremities and face?

Acromegaly

What larger polypeptide prohormone is processed to produce ACTH, MSH, and other neuroactive peptides?

POMC (Pro-opiomelanocortin)

Which anterior pituitary hormone stimulates the adrenal cortex to synthesize and secrete cortisol?

ACTH (Adrenocorticotropic Hormone)

What condition is characterized by symptoms caused by excessive levels of ACTH, often from a pituitary tumor?

Cushing's disease

What condition is caused by a deficiency in ACTH, leading to reduced cortisol secretion?

Addison's disease

What hypothalamic hormone stimulates the release of Thyroid-Stimulating Hormone (TSH)?

TRH (Thyrotropin-releasing hormone)

Which anterior pituitary glycoprotein hormone stimulates follicular development in the ovary and spermatogenesis in the testes?

FSH (Follicle-Stimulating Hormone)

Which anterior pituitary glycoprotein hormone triggers ovulation, luteinization, and stimulates testosterone/progesterone production?

LH (Luteinizing Hormone)

What hypothalamic hormone regulates the release of both FSH and LH?

GnRH (Gonadotropin-releasing hormone)

What transcription factor, when mutated, can lead to deficiencies in PRL, GH, and TSH cell development?

PIT-1

How does the hypothalamus communicate with the anterior pituitary gland?

Via releasing and inhibiting factors released into the primary capillary bed of the portal system

What two hormones are directly released by the posterior pituitary gland?

Oxytocin and Vasopressin (ADH)