The Thyroid Feedback Quantile-based Index (TFQI) is a calculated parameter for thyrotropic pituitary function. It was defined to be more robust to distorted data than established markers including

Jostel's TSH index Jostel's TSH index (TSHI or JTI), also referred to as Jostel's thyrotropin index or Thyroid Function index (TFI), is a method for estimating the thyrotropic (i.e. thyroid stimulating) function of the anterior pituitary lobe in a quantitative way. T ...

(JTI) and the thyrotroph thyroid hormone sensitivity index (TTSI).

How to determine the TFQI

The TFQI can be calculated with :

TFQI = F_(FT4) - (1 - F_(TSH))

from quantiles of FT4 and TSH concentration (as determined based on

cumulative distribution function In probability theory and statistics, the cumulative distribution function (CDF) of a real-valued random variable X, or just distribution function of X, evaluated at x, is the probability that X will take a value less than or equal to x. Ev ...

s). Per definition the TFQI has a mean of 0 and a

standard deviation In statistics, the standard deviation is a measure of the amount of variation or dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while ...

of 0.37 in a reference population. This explains the reference range of –0.74 to + 0.74.

Reference range

Clinical significance

Higher values of TFQI are associated with obesity,

metabolic syndrome Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Metabolic syndrome ...

, impaired renal function, diabetes, and diabetes-related

mortality Mortality is the state of being mortal, or susceptible to death; the opposite of immortality. Mortality may also refer to: * Fish mortality, a parameter used in fisheries population dynamics to account for the loss of fish in a fish stock throug ...

. In a large population of community-dwelling euthyroid subjects the thyroid feedback quantile-based index predicted all-cause mortality, even after adjustment for other established risk factors and comorbidities. A cross-sectional study from Spain observed increased prevalence of type 2 diabetes, atrial fibrillation, ischemic heart disease and hypertension in persons with elevated PTFQI. Serum Concentrations of Adipocyte Fatty Acid-Binding Protein (A-FABP) are significantly correlateted to TFQI, suggesting some form of cross-talk between adipose tissue and HPT axis. TFQI results are also elevated in

takotsubo syndrome Takotsubo cardiomyopathy or Takotsubo syndrome (TTS), also known as stress cardiomyopathy, is a type of non-ischemic cardiomyopathy in which there is a sudden temporary weakening of the muscular portion of the heart. It usually appears after a ...

, potentially reflecting type 2 allostatic load in the situation of psychosocial stress. Reductions have been observed in subjects with schizophrenia after initiation of therapy with oxcarbazepine and quetiapine, potentially reflecting declining allostatic load. Despite positive association to metabolic syndrome and type 2 allostatic load a large population-based study failed to identify an association to risks of dyslipidemia and non-alcoholic fatty liver disease (NAFLD).

References

{{Reflist, 2 Chemical pathology Blood tests Endocrine procedures Thyroidological methods Thyroid homeostasis Structure parameters of thyroid function Static endocrine function tests

How to determine the TFQI

Reference range

Clinical significance

See also

References