• Thyroid Gland
• Hyperthyroidism (Thyrotoxicosis)
• ECG and Hyperthyroidism (Thyrotoxicosis)

Thyroid Gland

• The thyroid gland (Glandula thyroidea) synthesizes thyroid hormones:
• Thyroxine (T4)
• Triiodothyronine (T3)
• The T4:T3 ratio is approximately 20:1. Therefore, only the level of T4 is measured
• Hypothalamic-pituitary axis:
• The hypothalamus synthesizes TRH
• TRH stimulates the pituitary gland, which synthesizes TSH
• TSH stimulates the thyroid gland, which synthesizes hormones T4, T3
• Synthesis operates on a feedback mechanism
  
  
• Hyperthyroidism
• Laboratory elevation of (T4, T3)
• It stimulates the body's metabolism
• Thyrotoxicosis
• Symptoms arise (e.g., tachycardia, fever, sweating...)
• Thyrotoxic storm
• It is an extreme form of thyrotoxicosis (temperatures 40°C, tachycardia, arrhythmias...)

ECG and Hyperthyroidism (Thyrotoxicosis)

• Main Signs
• Sinus Tachycardia
• Atrial Fibrillation (with a frequency > 100/min.)
  
  
• Secondary Signs:
• Supraventricular Tachycardia
• Atrial Extrasystoles
• Ventricular Extrasystoles
• Non-specific changes in the ST segment and T waves

Sinus Tachycardia

• Frequency: 150/min. (>100/min.)
• Sinus Tachycardia is a main sign of thyrotoxicosis

Thyrotoxicosis and Tachy-Fibrillation of the Atria

• Atrial Fibrillation
• Heart rhythm is irregularly irregular
• No P waves are visible
• Frequency: 150/min.
• The patient had laboratory results showing high T4 and low TSH