Summary/Abstract :
An oft repeated question in the pathophysiology of subclinical biochemical hyper hypo thyroidism is how does normal t3, t4 from thyroid manage to provide feedback to pituitary to increase or reduce the release of TSH from the pituitary!
The following UDLCO not only comes close to answering it but also provides a new angle in terms of individual driven precision medicine!
Glossary : https://userdrivenhealthcare.blogspot.com/2023/11/glossary-of-user-driven-healthcare.html?m=1
Conversational transcripts :
[11/9, 9:39 PM] CME India:
A woman complains of unintended weight loss, palpitations, and anxiety. Laboratories show low thyroid stimulating hormone and normal free T4. Which of the following is the most likely explanation for these findings?
A.
Central hypothyroidism
B.
Lab error
C.
T3 hyperthyroidism
D.
Surreptitious levothyroxine ingestion
[11/15, 12:25 PM] S S :
Subclinical hyperthyroidism
The value ranges of thyroid hormones are quite wide
Sometimes when the hyperthyroidism begins to occur, the T4 T3 may rise mildly, enough to cause beginning of mild symptoms, but numerically within normal range
The TSH however, has a relatively greater change which is visible numerically
Hence, subclinical thyroid disease occurs
Usually, these progress further, and overt disease results
[11/22, 8:06 PM] Rakesh Biswas: Any reference to these statements about t3, t4 rising mildly but numerically within normal range? 🙂🙏
[11/22, 8:34 PM] SS : Above is the reference for my statement
An excellent article talking about how to interpret thyroid function tests
Gives all unusual circumstances which sometimes lead to discordant TFTs
[11/22, 8:48 PM] Rakesh Biswas:
Thanks.
In this write up, while the first line does have an in text citation with reference 3, the more important shaded line appears to be without a reference and is perhaps the author's opinion?
[11/22, 9:31 PM] A P : There is a linear inverse relationship between the serum free T 4 concentration and the log of the TSH , making the serum TSH concentration an exquisitely sensitive indicator of the thyroid state of patients with an intact hypothalamic-pituitary axis.
[11/22, 9:31 PM] AP : Williams Textbook of Endocrinology
11/22, 9:33 PM] AP : The log/linear relationship between thyroid-stimulating hormone (TSH) (on the vertical axis) and the free T 4 concentrations (FT 4 ). Typical free T 4 concentrations in hypothyroid, euthyroid, and hyperthyroid patients are shown.
[11/22, 9:19 PM] S S : One of the cross references
[11/22, 9:30 PM] Rakesh Biswas:
Thanks. It looks promising.
Can you share the online URL to this article or text the title here so that I can try to get the full text?
[11/22, 9:32 PM] S S :
The link 👆
[11/22, 9:49 PM] Rakesh Biswas: Thanks for this very interesting study and conclusion that perhaps throws a new light onto our belief systems on how each one of us perceives "subclinical hypothyroidism" and I quote,
"The individual reference ranges for test results were narrow, compared with group reference ranges used to develop laboratory reference ranges. Accordingly, a test result within laboratory reference limits is not necessarily normal for an individual. Because serum TSH responds with logarithmically amplified variation to minor changes in serum T(4) and T(3), abnormal serum TSH may indicate that serum T(4) and T(3) are not normal for an individual. A condition with abnormal serum TSH but with serum T(4) and T(3) within laboratory reference ranges is labeled subclinical thyroid disease. Our data indicate that the distinction between subclinical and overt thyroid disease (abnormal serum TSH and abnormal T(4) and/or T(3)) is somewhat arbitrary. For the same degree of thyroid function abnormality, the diagnosis depends to a considerable extent on the position of the patient's normal set point for T(4) and T(3) within the laboratory reference range."
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