Topic: coagulation disorders, leukemia, Hypo and hyper thyrodism, meningitis and encephalitis.
Question: A 25 year old female has presented to the medicine OPD with complaints of excessive tierdness, cold intolerance and menstrual irregularities. ① Write the name of thyroid disorder that can lead to above manifestations. ② Tabulate the differentiating cardio- vascular clinical manifestations in hypothyroidism and hyperthyroidism?
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① The thyroid disorder that can lead to the above manifestations is hypothyroidism.
② Differentiating cardiovascular clinical manifestations in hypothyroidism and hyperthyroidism:
Hypothyroidism and hyperthyroidism have opposite effects on the cardiovascular system. In hypothyroidism, there is a decrease in cardiac output, bradycardia, increased systemic vascular resistance, and a decrease in blood pressure. While in hyperthyroidism, there is an increase in cardiac output, tachycardia, decreased systemic vascular resistance, and an increase in blood pressure.
Hypothyroidism:
Bradycardia: Due to decreased sensitivity of sinus node and AV node to catecholamines. Heart rate <60 beats/min.
Peripheral vasoconstriction: Decreased cardiac output leads to vasoconstriction. This causes cold intolerance and decreased peripheral perfusion.
Hypertension: Occurs in 20-30% of patients. Due to increased systemic vascular resistance.
Dyslipidemia: Increased total and LDL cholesterol due to decreased catabolism.
Hyperthyroidism:
Tachycardia: Increased sensitivity of sinus node and AV node to catecholamines. Heart rate >100 beats/min.
Peripheral vasodilation: Increased cardiac output leads to vasodilation. This causes warm intolerance and increased peripheral perfusion.
Systolic hypertension: Occurs in some patients due to increased cardiac output.
Atrial fibrillation: Especially in older patients. Due to increased automaticity.
Dyslipidemia: Decreased total and LDL cholesterol due to increased catabolism.
Investigations:
- Thyroid Function Test (TFT): This test measures the levels of thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) in the blood. Reference values are as follows: – TSH: 0.4 – 4.0 mIU/L – FT4: 9.0 – 25.0 pmol/L – FT3: 3.5 – 7.8 pmol/L
- Thyroid autoantibodies: Anti-thyroid peroxidase (anti-TPO) anti-thyroglobulin (anti-Tg) antibodies can be measured to determine if the cause of hypothyroidism is autoimmune (e.g., Hashimoto’s thyroiditis).
- Imaging: Thyroid ultrasound or radioactive iodine uptake scan may be performed to assess the size, shape, and function of the thyroid gland.
- ECG: Bradycardia in hypothyroidism, tachycardia and atrial fibrillation in hyperthyroidism.
- Echocardiography: May show pericardial effusion in some patients.
- Stress test: Decreased exercise tolerance in hypothyroidism, increased in hyperthyroidism.
Treatment:
Hypothyroidism: Levothyroxine replacement. Start with 25-50 mcg/day and titrate by 25 mcg every 3-4 weeks based on TSH levels. Target TSH: 0.5-2 mIU/L.
Hyperthyroidism: Antithyroid drugs such as Methimazole and Propylthiouracil, Beta-blockers like Propranolol, Calcium channel blockers like Verapamil can be used. Radioiodine therapy and thyroidectomy can also be used in certain cases.
Dosage: As mentioned above for Levothyroxine. Carbimazole: 15-40 mg/day in 2-3 divided doses. Propranolol: 40 mg twice daily, titrated based on heart rate.
Table summarizing the differences between Hypothyroidism and Hyperthyroidism:
| Parameters | Hypothyroidism | Hyperthyroidism |
|---|---|---|
| Heart Rate | Bradycardia | Tachycardia |
| Cardiac Output | Decreased | Increased |
| Systemic Vascular Resistance | Increased | Decreased |
| Blood Pressure | Decreased | Increased |
| Atrial Fibrillation | Not common | Common |
Overall, the diagnosis and management of thyroid disorders require a comprehensive approach that includes a detailed history, clinical examination, and relevant investigations. Early detection and appropriate management can prevent complications and improve patient outcomes.
