Thyroid Function Interpreter

Low PTFQI means that TSH is lower than expected for the given FT4, reflecting apparent pituitary over-sensitivity or impaired TSH secretion. Very low values may support a diagnosis of central (secondary/tertiary) hypothyroidism.

High PTFQI indicates TSH is higher than expected for the given FT4, most commonly seen in subclinical hypothyroidism or reduced apparent pituitary sensitivity.

Low TSHI means that TSH is lower than expected for the given FT4, reflecting apparent pituitary over-sensitivity or impaired TSH secretion. Very low values may support a diagnosis of central (secondary/tertiary) hypothyroidism.

High TSHI indicates TSH is higher than expected for the given FT4, most commonly seen in subclinical hypothyroidism or reduced apparent pituitary sensitivity.

Low SPINA-GT indicates reduced thyroid secretory capacity.

• Primary hypothyroidism
• Autoimmune thyroiditis (Hashimoto's)
• Iodine deficiency

Elevated SPINA-GT indicates increased thyroid secretory capacity.

• Primary hyperthyroidism
• Graves' disease
• It has been observed to positively correlate to resting energy expenditure, resting heart rate, the colour Doppler ultrasound pattern and thyroid volume.

Low SPINA-GD indicates reduced peripheral T4-to-T3 conversion.

High SPINA-GD indicates increased peripheral T4-to-T3 conversion.

A low FT3/FT4 ratio indicates relatively low FT3 compared with FT4.

• Common in patients on T4-only monotherapy (Levothyroxine).
• With normal FT4 and TSH: poor peripheral conversion. Seen in: Insufficient Selenium or Zinc, Chronic inflammation, high cortisol/stress, or caloric restriction.
• Decreased ratio seen in unhealthy aging (often with high BMI).
• Very low ratio seen in non-thyroidal illness (acute or chronic systemic disease).

A high FT3/FT4 ratio indicates relatively high FT3 compared with FT4.

• Common in patients taking T3-containing medication.
• With low FT4 and/or high TSH: untreated early Hashimoto’s hypothyroidism. Compensatory mechanism via upregulating D2 enzyme (enhancing peripheral T4-T3 conversion rate) and TSH receptor stimulation (increasing the T3/T4 ratio produced by the thyroid gland).
• With elevated FT4 and TSH < 0.01: untreated early Graves’ hyperthyroidism. TSH-receptor stimulating antibodies are hijacking TSH receptors and disproportionately increasing T3 production (often differentiates Graves' from thyroiditis).
• With low or "inappropriately normal" TSH: Central hypothyroidism.
• Elevated FT3/FT4 ratio is also seen in some euthyroid individuals with obesity, insulin resistance, or metabolic syndrome.

Shift toward increased thyroid hormone inactivation (higher rT3, lower T3) is driven by systemic illness, inflammation, energy deficit, or organ dysfunction rather than an "thyroid problem".

Shift toward decreased thyroid hormone inactivation (lower rT3, higher T3).

• With low PTFQI it is supportive of central hypothyroidism.