Hormones
T4 / TSH Ratio
What This Marker Tells Us
Compares thyroid hormone output to the pituitary signal requesting it, revealing how efficiently your thyroid responds to stimulation and peripheral hormone conversion.
Why It Matters
This ratio detects subtle thyroid dysfunction missed by TSH or T4 alone. When T4 is low relative to TSH, your thyroid underresponds to stimulation. When T4 is high relative to TSH, either your pituitary under-signals despite adequate hormone or peripheral conversion issues exist. The ratio reveals the thyroid-pituitary feedback loop's efficiency, guiding diagnosis and treatment before overt disease develops.
How to Interpret Your Trends
Low ratios suggest hypothyroidism, thyroid resistance, or inadequate thyroid response to TSH stimulation. Typical ratios indicate normal thyroid-pituitary axis function with efficient hormone production and feedback. High ratios may suggest central hypothyroidism (pituitary issue), thyroid hormone resistance, or early hyperthyroidism. Very high ratios with low TSH confirm hyperthyroidism with suppressed pituitary signaling.
What Influences This Marker
Iodine deficiency, selenium deficiency, autoimmune thyroid disease, and certain medications impair T4 production, lowering the ratio. Pituitary dysfunction affects TSH production. Chronic stress, calorie restriction, and illness alter the ratio temporarily. Adequate iodine and selenium, treating autoimmunity, and supporting overall health normalize thyroid function.
How Your Team Uses It
Your team uses this ratio to detect thyroid dysfunction earlier than individual markers, guiding further testing and intervention. Low ratios prompt thyroid antibody testing and nutrient optimization. It helps distinguish between thyroid gland issues and pituitary dysfunction, directing appropriate treatment strategies.
Related Signals We Also Review
TSH, total T4, free T4, T3, reverse T3, thyroid antibodies, selenium, and iodine status complete the thyroid function assessment.