Endocrine

Endocrine System Overview

  • The endocrine system plays a crucial role in regulating various body functions through hormones released into the bloodstream.

Problem Based Medical Diagnosis: DAMN IT VP

Acronym Breakdown

  • D – Degenerative

  • A – Allergic, Anomalous

  • M – Metabolic (Malformation)

  • N – Neoplasia (Nutritional)

  • I – Infection, Inflammation, Immune-mediated, Iatrogenic/Idiopathic

  • T – Trauma, Toxicity

  • V – Vascular

  • P – Parasitic

Central Nervous System & Hormonal Feedback

Feedback Mechanisms

  • Short Feedback Loop

    • Involves hormones released from the hypothalamus affecting the anterior pituitary and vice versa.

  • Long Feedback Loop

    • Involves the target organs responding to the hormones released by the anterior pituitary.

  • Ultra-Short Feedback Loop

    • Hormones may directly inhibit their own release from the hypothalamus or pituitary.

Hormonal Regulation

  • Hypothalamus

    • Releases hormones and factors that regulate the anterior pituitary.

  • Tropic Hormones

    • Hormones from the anterior pituitary affecting target organs.

Hypothalamic-Pituitary-Thyroid Axis

  • Hypothalamus releases TRH to stimulate the anterior pituitary.

  • Anterior Pituitary produces TSH that stimulates the Thyroid.

  • Thyroid Gland produces T4 and T3 hormones with multiple physiological effects.

Thyroid Dysfunction

Hypothyroidism

  • Definition: Underproduction of thyroid hormones.

  • Causes: Thyroid atrophy or thyroiditis.

  • Demographics: Common in middle-aged female dogs; breed predilection.

  • Clinical Signs: Weight gain, poor hair coat, recurrent skin issues.

  • Diagnosis: High cholesterol, low T3/T4, elevated TSH.

  • Treatment: Thyroid hormone supplementation; annual rechecks required.

Hyperthyroidism

  • Definition: Overproduction of thyroid hormones.

  • Causes: Thyroid adenoma (neoplasia).

  • Demographics: Most common in older cats.

  • Clinical Signs: Weight loss, increased appetite, tachycardia.

  • Diagnosis: Increased T4 levels.

  • Treatment: Surgery, anti-thyroid medications (methimazole), radioactive iodine.

Adrenal Gland Disorders

Hormones

  • Mineralocorticoids: Regulate electrolyte balance.

  • Glucocorticoids: Affect metabolism and stress response (e.g., cortisol).

  • Androgens and Estrogens: Influence secondary sexual characteristics.

  • Catecholamines: Epinephrine and norepinephrine involved in fight or flight response.

Hypoadrenocorticism (Addison's Disease)

  • Definition: Underproduction of adrenal hormones.

  • Demographics: Rare; middle-aged female dogs, especially standard poodles and labs.

  • Clinical Signs: Non-specific symptoms, vomiting, PU/PD.

  • Diagnosis: Electrolyte imbalances; ACTH Stimulation test.

  • Treatment: Corticosteroid supplementation.

Hyperadrenocorticism (Cushing's Disease)

  • Definition: Overproduction of adrenal hormones.

  • Causes: Pituitary/hormonal tumors.

  • Demographics: Middle-aged dogs.

  • Clinical Signs: Polyphagia, abdominal distension, alopecia.

  • Diagnosis: Elevated liver enzymes, glucose, and cortisol; ACTH Stimulation test.

  • Treatment: Surgery, adrenal suppressants (Lysodren, Trilostane).

Diabetes Mellitus

Overview

  • Definition: Impaired insulin production (Type 1) or functioning (Type 2).

  • Demographics: Common in dogs (100% Type 1) and cats (50% Type 1, 50% Type 2).

  • Clinical Signs: PU/PD, weight loss with polyphagia, dehydration.

  • Diagnosis: Fasting blood glucose >200 mg/dl.

  • Treatment: Insulin injections, dietary management, owner education.

Insulinoma

  • Definition: Tumor causing overproduction of insulin.

  • Clinical Signs: Hypoglycemia, weakness, ataxia.

  • Diagnosis: Low blood glucose; increased insulin levels.

  • Treatment: Manage hypoglycemia; small frequent meals; surgical intervention may be required.

Parathyroid Disorders

Hypoparathyroidism

  • Definition: Underproduction of parathyroid hormones.

  • Causes: Often secondary to thyroid surgery.

  • Clinical Signs: Muscle tremors, weakness, hypocalcemia symptoms.

  • Diagnosis: Low calcium levels; history assessment.

  • Treatment: Vitamin D and calcium supplements.

Hyperparathyroidism

  • Definition: Overproduction of parathyroid hormone.

  • Demographics: Common in middle-aged to older dogs.

  • Clinical Signs: Hypercalcemia-related symptoms (PU/PD, vomiting).

  • Diagnosis: Elevated serum calcium, low phosphorus.

  • Treatment: Surgical intervention.