SPINA-GD Calculator

Peripheral Deiodinase Activity (T4 to T3 Conversion)

TSH (µIU/mL or mIU/L):

Note: 1 µIU/mL = 1 mIU/L (equivalent units)

Free T3 (pmol/L):

Free T4 (pmol/L):

β (Default = 1.1):

D (Default = 0.3):

SPINA-GD Formula: (FT3 / FT4) × (β / (1 + TSH / D))

Results:

SPINA-GD: nmol/s

Interpretation:

Clinical Significance:

Estimates peripheral deiodinase activity (T4 to T3 conversion)
Reflects overall thyroid hormone metabolism efficiency

Reference Ranges:

Normal: ~20-40 nmol/s
Low: Possible deiodinase deficiency (hypothyroidism, selenium deficiency)
High: Increased conversion (hyperthyroidism, inflammation)

Parameters:

β = 1.1 (typical value for euthyroid subjects)
D = 0.3 (typical value for euthyroid subjects)

Source: Dietrich JW, et al. (2016). "SPINA Thyr: A Novel Systems Theoretic Approach to Determine the Secretion Capacity of the Thyroid Gland."