Flashcards: Endocrine System

Endocrine System Overview

Front: What is the endocrine system composed of?
Back: Groups of tissues that form organs

Front: How do endocrine tissues release hormones?
Back: They are ductless and release hormones directly into circulation

Front: What is a hormone?
Back: A signaling molecule

Front: What are the three types of hormones?
Back: Protein hormones, steroid hormones, modified amino acid hormones

Front: How do hormones function?
Back: Travel to distant targets, interact with receptors, and create effects

Front: What do hormones control?
Back: Biological processes and most tissues

Front: Is endocrine dysfunction common?
Back: Yes

Types of Hormones

Protein & Polypeptide Hormones

Front: Where are protein hormones produced?
Back: In endocrine tissues via gene transcription

Front: What triggers protein hormone release?
Back: Specific signals (e.g., insulin secretion with increased glucose)

Front: Are protein hormones stored in large amounts?
Back: Yes, for quick release

Front: How do protein hormones act on target cells?
Back: Bind to cell surface receptors

Front: What happens if receptor mutations occur?
Back: Diseases arise (e.g., inactivation or nonhormonal pathway activation)

Steroid Hormones

Front: What are steroid hormones derived from?
Back: Cholesterol

Front: Where are steroid hormones produced?
Back: Adrenal cortex, ovaries, testes

Front: Are steroid hormones stored in large amounts?
Back: No, they are synthesized rapidly as needed

Front: Are steroid hormones hydrophobic or hydrophilic?
Back: Hydrophobic; they easily pass through cell membranes

Front: How are steroid hormones transported in blood?
Back: By carrier proteins

Front: How do steroid hormones act compared to protein hormones?
Back: Slower onset but longer-lasting effects

Modified Amino Acid Hormones

Front: What are modified amino acid hormones derived from?
Back: Tyrosine

Front: Give examples of modified amino acid hormones.
Back: Thyroid hormones, epinephrine, norepinephrine

Front: How are modified amino acid hormones transported?
Back: Via carrier proteins (mostly water-insoluble)

Front: Where do modified amino acid hormones act?
Back: Intracellular receptors

Front: What is the half-life of modified amino acid hormones?
Back: Short (<5 min)

Endocrine Disorders

Hypertrichosis (Cushing’s Syndrome) in Horses

Front: What causes Cushing’s Syndrome in horses?
Back: Pituitary Pars Intermedia Dysfunction (PPID) – adenoma of the pars intermedia

Front: How does Cushing’s affect the hypothalamus?
Back: Alters body temperature, appetite, shedding

Front: What is the pathognomonic sign of Cushing’s in horses?
Back: Long, curly hair coat

Front: What are other clinical signs of Cushing’s?
Back: PU/PD, muscle weakness, abnormal fat distribution, increased infections

Front: How is Cushing’s diagnosed?
Back: ACTH concentrations, blood cortisol response, thyrotropin-releasing hormone (TRH) test

Front: What is the treatment for Cushing’s?
Back: Pergolide (dopaminergic receptor agonist), body hair clipping, supportive care

Hyperthyroidism in Horses

Front: Is hyperthyroidism in horses commonly misdiagnosed?
Back: Yes

Front: What are the two types of hyperthyroidism?
Back:

• Primary: Thyroid gland dysfunction

• Secondary: Anterior pituitary dysfunction → low TSH

Front: What are clinical signs of hyperthyroidism in foals?
Back: Weakness, poor suckling, fine hair coat, tendon laxity, low body temperature

Front: What are clinical signs of hyperthyroidism in adult horses?
Back: Lethargy, low heart rate, obesity, laminitis, exercise intolerance

Front: How is hyperthyroidism diagnosed?
Back: Thyroid hormone levels (unreliable), TRH response test, response to hormone supplementation

Front: What is the treatment for hyperthyroidism?
Back: Thyroid hormone supplementation (weaning required)

Hypothyroidism in Sheep/Goats (Goiter)

Front: What causes hypothyroidism in sheep/goats?
Back: Iodine deficiency, thyrotoxic plants

Front: What happens when T3/T4 levels are low?
Back: Increased TSH → thyroid gland enlargement

Front: What are the clinical signs of hypothyroidism in sheep/goats?
Back: Poor wool quality, dry skin, tendon laxity, poor reproductive performance

Front: How is hypothyroidism diagnosed?
Back: Clinical signs + low iodine levels

Front: What is the treatment for hypothyroidism?
Back: Iodine supplementation

Hyperparathyroidism

Front: What causes hyperparathyroidism?
Back: Nutritional imbalance (Ca:P ratio), oxalate-rich plants, iatrogenic causes

Front: What hormone is involved in hyperparathyroidism?
Back: Parathyroid hormone (PTH) → bone calcium resorption

Front: What are clinical signs of hyperparathyroidism?
Back: Lameness, loose teeth, spontaneous fractures, inability to rise

Front: How is hyperparathyroidism diagnosed?
Back: Radiographs, dietary analysis

Front: How is hyperparathyroidism treated?
Back: Correct mineral imbalance, prevent with proper diet