Hyperthyroidism vs. Hypothyroidism

Introduction

• Video covers hyperthyroidism and hypothyroidism
• Discusses symptoms and their underlying causes
• Reviews thyroid hormone function
• Encourages watching the entire video for a complete understanding

Thyroid Hormone Production and Regulation

Pathway

• Hypothalamus: Releases thyrotropin-releasing hormone (TRH)
  • Located in the brain below the thalamus
• Pituitary Gland:
  • TRH stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH)
  • TSH enters the bloodstream
• Thyroid Gland:
  • TSH binds to the thyroid gland (butterfly-shaped structure in neck)
  • Activates production of thyroid hormones (T3 - triiodothyronine, and T4 - thyroxine)
• Regulation:
  • Negative feedback loop: High thyroid hormone levels inhibit TRH and TSH release. Low levels decrease inhibition to increase TRH and TSH production

Memory Aids

• HPT Axis:
  • H (Hypothalamus) → P (Pituitary) → T (Thyroid)
• Hormones: TRH before TSH:
  • R in TRH comes before S in TSH alphabetically

Effects of Thyroid Hormone on the Body

General Impact

• Increases protein synthesis
• Increases metabolic activity
• Generates body heat (thermogenesis)

Specific Organs

1. Heart:
   • Increases beta-1 adrenergic receptors
   • Increases heart rate, cardiac contraction, stroke volume, and blood pressure
2. GI System:
   • Increases metabolic activity
   • Increases GI motility and secretions
3. Central Nervous System:
   • Increases neurogenesis, myelination, synaptogenesis, and dendrite formation
   • Enhances mood and cognition in adults
4. Sympathetic Nervous System:
   • Increases overall activity
5. Skin, Hair, and Nails:
   • Increases cutaneous blood flow
   • Stimulates skin cell proliferation
   • Increases sweat, hair growth, and nail growth

Hyperthyroidism

Definition

• Overactive thyroid gland producing excessive thyroid hormone

Symptoms

• Hypermetabolic State:
  • Weight loss
  • Increased appetite
  • Increased body temperature and heat intolerance
• Heart:
  • Tachycardia, palpitations, arrhythmias, and hypertension
• GI System:
  • Diarrhea
• CNS and Sympathetic System:
  • Anxiety, nervousness, irritability, restlessness, insomnia, tremors, hyperreflexia
• Skin, Hair, Nails:
  • Sweating, fine and soft hair, onycholysis, increased skin secretions
• Other Symptoms:
  • Shortness of breath
  • Fatigue
  • Muscle weakness
  • Osteoporosis

Hypothyroidism

Definition

• Underactive thyroid gland producing insufficient thyroid hormone

Symptoms

• Hypometabolic State:
  • Weight gain
  • Decreased appetite
  • Decreased body temperature and cold intolerance
• Heart:
  • Bradycardia, hypertension (due to vasoconstriction and increased peripheral resistance)
• GI System:
  • Constipation
• CNS and Sympathetic System:
  • Fatigue, depression, mental fog, impaired memory and concentration, delayed deep tendon reflexes
• Skin, Hair, Nails:
  • Dry and pale skin, hair loss, coarse and brittle hair, thin and brittle nails
• Other Symptoms:
  • Hoarse voice
  • Muscle cramps
  • Joint pain

Summary

• Hyperthyroidism: Ramps up body functions
• Hypothyroidism: Slows down body functions
• Table summarizing differences is available in the lecture notes and study guide

Closing

• Encourage likes, comments, and subscriptions
• Notes and study guides are linked below
• Thanks for watching and future video recommendations