Interpretation of Thyroid Function Tests in Hypothyroidism and Hyperthyroidism

Understanding Thyroid Disorders

The thyroid gland plays a crucial role in regulating metabolism, energy levels, and overall body function. Any imbalance in thyroid hormones can lead to hypothyroidism or hyperthyroidism.

Types of Thyroid Disorders

Primary Thyroid Disorders

Primary thyroid disorders originate from dysfunction within the thyroid gland. The most common conditions include:

• Primary Hypothyroidism: Characterized by elevated TSH levels and low free T4.
• Primary Hyperthyroidism: Defined by suppressed TSH and elevated free T4 or T3 levels.

Secondary Thyroid Disorders

These disorders occur due to pituitary dysfunction affecting TSH secretion.

• Secondary Hypothyroidism: Low TSH and low free T4 due to pituitary failure.
• Secondary Hyperthyroidism: Excess TSH secretion leading to elevated free T4.

Subclinical Thyroid Disorders

These are early stages of thyroid disease where hormone levels are mildly altered but symptoms may not be evident.

• Subclinical Hypothyroidism: Elevated TSH with normal free T4.
• Subclinical Hyperthyroidism: Suppressed TSH with normal free T4 and T3.

Interpreting Thyroid Function Tests

Common Laboratory Markers

• TSH (Thyroid-Stimulating Hormone): Elevated in hypothyroidism, suppressed in hyperthyroidism.
• Free T4 (Thyroxine): Low in hypothyroidism, high in hyperthyroidism.
• Free T3 (Triiodothyronine): Often elevated in hyperthyroidism.
• Thyroid Antibodies: Useful in diagnosing autoimmune thyroid conditions such as Hashimoto’s and Graves' disease.

Conclusion

Thyroid function tests provide critical insights into thyroid health. Proper interpretation helps differentiate primary, secondary, and subclinical thyroid disorders, enabling timely diagnosis and treatment.