Endocrine Glands | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Thyroid Disorders

Hypothyroidism

• Cretinism Symptoms:
  • Iodine deficiency in immature animals.
  • Exhaustion of thyroid gland.
  • Failure to grow, irreversible CNS dysfunction, mental dullness.
  • Dry, brittle coat, thin skin, scaly-ness, dermatitis, possibly obesity.
  • Lethargy, hypercholesteremia.
• Myxedema Symptoms:
  • Iodine deficiency in mature animals.
  • Similar symptoms to cretinism.

Hyperthyroidism

• Types: Parenchymatous goiter, cellaid goiter, nodular or adenomatous goiter, exophthalmic goiter, or thyroiditis.
• Thyrotoxicosis: Excess thyroxin production.
• Symptoms: Nervousness, irritability, weight loss, increased appetite, cardiac irregularity.

Diagnosis

• Characteristic symptoms.
• Thyroid function tests:
  • Basal Metabolic Rate (BMR).
  • Iodine uptake.
  • Serum protein-bound iodine.
  • Total serum T4.
  • T3 response uptake.
  • Thyroid-stimulating hormone (TSH) response tests.
  • Cholesterol level.
  • Thyroid biopsy.

Parathyroid Disorders

Hypoparathyroidism

• Rare in domestic animals, seen in dogs.
• Symptoms: Neuromuscular excitability, tetany.
• May progress to generalized tetany and convulsive seizures.
• Diagnosis: Low blood calcium levels (4-5 mg/dl).

Hyperparathyroidism

• Primary hyperparathyroidism in dogs.
• Symptoms: Fibrous osteodystrophy, bone fractures, deformities.
• Chronic condition may lead to kidney stone formation.
• Secondary hyperparathyroidism secondary to chronic renal disease.
• Hypocalcemia leads to rubber jaw or fibrous osteodystrophy, chronic demineralization of osseous tissue.

Diagnosis of Endocrine Disorders

Pituitary Gland

• Underproduction (Hypopituitarism):
  • Pituitary dwarfism in immature animals.
  • Reduced activity in other target organs.
  • Dysfunction leads to hypothyroidism, hypogonadism, and hypoadrenocortical function.
  • Diagnosis: Based on characteristic symptoms.
• Overproduction:
  • Lengthening of long bones and increased soft tissue.
  • Acromegaly.
  • Diagnosis: Based on symptoms.

Adrenal Gland

• Hypofunction (Addison's Disease):
  • Acute or chronic hypofunction.
  • Symptoms: Weakness, low blood pressure, pigmentation of skin, vomiting, diarrhea, loss of appetite, atrophied thyroid, water and sodium loss, acidosis.
  • Diagnosis: Based on characteristic symptoms.
• Hyperfunction (Cushing's Syndrome):
  • Symptoms: Painful adiposity, muscle wasting, amenorrhea, osteoporosis, skin atrophy, hypertension, hyperglycemia, sodium retention, susceptibility to infection, potbelly, dermatitis, adrenal virilism.
  • Diagnosis: Based on characteristic symptoms.

Thymus

• Hyperplasia:
  • Underdevelopment of adrenal and cardiovascular system.
  • Lowered resistance to infections (status thymolymphaticus).
  • Seen in dogs, cats, and cattle.
• Dysfunction and Diseases:
  • Defective thymus leads to haemolytic anemia and systemic lupus erythematosus in animals.
  • Myasthenia gravis in humans, causing muscular weakness.
  • Thymomas (tumors) may cause functional dysfunction, sometimes spreading to lungs, pericardium, lymph nodes.
  • Lymphosarcoma or Hodgkin's disease in young animals.

Pineal Gland

• Hyperfunction: Associated with delayed puberty.
• Hypofunction: Associated with precocious puberty.
• Destruction by Tumor: Causes cachexia, trophic disturbances, adiposity, premature development of genital organs, premature spermatogenesis, and growth of interstitial cells.
• Diagnosis: Based on symptoms.

Pancreas

• Functional Disorders:
  • Hyperinsulinism: Causes hypoglycemia.
  • Diabetes Mellitus: Causes hyperglycemia.
• Symptoms of Hyperinsulinism (in dogs):
  • Dysfunction of the nervous system due to hypoglycemia.
  • Incoordination, dizziness, muscular weakness, tremors, loss of consciousness, convulsions.
• Symptoms of Diabetes Mellitus (in dogs and cats):
  • Older animals, especially females, develop cataracts.
• Diagnosis: Based on symptoms.

Synthesis of Hormones

Pineal Gland

Melatonin Synthesis:

• The pineal gland synthesizes melatonin using the enzyme hydroxyindole-o-methyltransferase.
• Melatonin is crucial for skin health.

Thyroid Gland

Thyroid Hormone Synthesis:

• Involves the concentration of iodide and synthesis of thyroid hormones.
• Iodine is trapped in the thyroid gland, oxidized, and iodinated amino acids are formed.
• Thyroid hormones include thyroxine (T4) and triiodothyronine (T3).
• Synthesis occurs in the colloid protein thyroglobulin.

Parathyroid Gland

Parathormone (PTH) Synthesis:

• Initially synthesized as proparathormone, a larger molecule.
• Biologically active PTH includes 84 amino acids.
• Secreted into the bloodstream from parathyroid cells.

Pancreas

Insulin and Glucagon Synthesis:

• Islets of Langerhans in the pancreas secrete insulin and glucagon.
• Insulin helps lower blood sugar, while glucagon raises it.
• Discovered by Banting and Best in 1921.