Investigating Patient Symptoms

The patient presents with a constellation of symptoms including:

• Menstrual irregularity
• Weight gain
• Hair loss
• Tiredness and weakness

This combination of symptoms commonly suggests potential thyroid dysfunction, particularly hypothyroidism.

Choosing the Investigation of Choice

For suspected thyroid disorders, the most appropriate initial investigation is measuring Thyroid Stimulating Hormone (TSH) along with a measure of thyroid hormone availability, typically Free T4.

• TSH (Thyroid Stimulating Hormone): This pituitary hormone regulates thyroid function. It is the most sensitive indicator for diagnosing primary hypothyroidism (high TSH, low T4) and hyperthyroidism (low TSH, high T4).
• Free T4 (Thyroxine): This is the active form of the main thyroid hormone. Measuring it alongside TSH helps confirm the diagnosis and assess the severity of thyroid dysfunction.

While FSH, LH, and Estrogen levels relate to reproductive function, they do not directly explain the cluster of symptoms like weight gain and fatigue as effectively as thyroid tests do. Free T3 is sometimes used but Free T4 and TSH are the standard initial panel.

Therefore, measuring Free T4 and TSH level is the investigation of choice.