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Clinical · Bloodwork · continued

eGFR fluctuation and the creatinine denominator problem — the long version posts 31–48

This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.

DS
dr_seongTL3Physician24 Jul 2026#31

TSH and free hormones: TSH is a reasonable screening test but does not tell you about actual free hormone levels. If TSH is abnormal, free thyroid hormones confirm whether there is a real thyroid problem.

22 likes 4d
RF
ro.friskTL224 Jul 2026#32

An honest declaration on egfr fluctuation: I have a prior here and it is strong enough that you should weight what I say downward. Stating it rather than hiding it.

0 likes 4d
CL
customs_ledgerTL3Regular24 Jul 2026#33
r.serrano, post #8: Glycaemic markers integrate over different periods. A point glucose and a longer-term marker disagreeing is not a contradiction; it is two different questions. Happy to be the one who is wrong here if it settles the question. Go to post

That is clearer than the version I had in my head. Thank you.

2 likes in reply to #8 4d
FW
f.weissTL224 Jul 2026#34
ne.laurent, post #16: Time of day: some biomarkers vary across the day. Cortisol in the morning differs from cortisol in the evening. Comparing results from different times of day is comparing things that are not the same. Go to post

Post #32 and I disagree about the size of the effect, not about the direction.

Trying to state the egfr fluctuation position in a way that someone who disagrees would recognise as fair, because I do not think the version in this thread passes that test.

9 likes in reply to #16 4d
WN
w.novakTL325 Jul 2026#35
TK
t.karlsenTL225 Jul 2026#36

An update on my earlier egfr fluctuation post: the pattern held for another six weeks and then stopped, which I did not predict and cannot explain.

30 likes 3d
ST
slow_titratorTL2Regular25 Jul 2026#37
n.bridgewater, post #13: If someone has run egfr fluctuation properly I would rather read that than my own reconstruction of it. Posting mine only because the thread has gone quiet. Go to post

This follows post #34 rather than contradicting it.

Distinguishing three things in the egfr fluctuation discussion that keep getting used interchangeably: the observation, the proposed mechanism, and the recommendation that gets attached to both.

1 like in reply to #13 3d
HE
h.espinozaTL225 Jul 2026#38
glossary_desk, post #21: Egfr fluctuation has a well-known answer and a correct answer, and the interesting work is establishing that they are the same. Nobody has done that here yet. Go to post

Time of day: some biomarkers vary across the day. Cortisol in the morning differs from cortisol in the evening. Comparing results from different times of day is comparing things that are not the same.

6 likes in reply to #21 3d
MN
m.ndiayeTL226 Jul 2026#39

What I would tell a new member reading about egfr fluctuation for the first time: the confident posts are not the reliable ones, and the reliable ones are longer.

0 likes 2d
HK
h.kjeldsenTL1Member26 Jul 2026#40

Coming back to post #36, because the follow-up matters more than the original answer.

Egfr fluctuation would be much easier to settle if anyone reported the denominator. Almost nobody reports the denominator.

0 likes 2d
EM
e.mensaTL226 Jul 2026#41

Understood. Thank you for being specific about the limits of it.

16 likes 2d
VD
vial_deskTL3Regular26 Jul 2026#42

Picking up post #40: that is the part I would want checked first.

A trend needs at least three points to be a trend. Two points are a line and a line through noise is still a line.

It is the kind of thing that is obvious once and never again.

6 likes 1d
PO
pe.onwukaTL227 Jul 2026#43
dr_seong, post #31: TSH and free hormones: TSH is a reasonable screening test but does not tell you about actual free hormone levels. If TSH is abnormal, free thyroid hormones confirm whether there is a real thyroid problem. Go to post

What I would want before treating egfr fluctuation as settled: the method, the sample, and whether anyone tried to find the opposite result. Two of the three are usually missing.

1 like in reply to #31 1d
AR
ambient_reviewTL3Regular27 Jul 2026 · edited#44

My experience of egfr fluctuation contradicts the reply above. I am posting it as a data point rather than as a refutation, because one person's experience is exactly that.

0 likes 23h
GE
g.ekstromTL227 Jul 2026#45

Post #42 describes the usual case. This is about the unusual one.

Glycaemic markers integrate over different periods. A point glucose and a longer-term marker disagreeing is not a contradiction; it is two different questions.

That is the honest state of it as of this week.

23 likes 18h
L
LeitermanTL3Regular27 Jul 2026#46

Renal function markers: eGFR is estimated, not measured. It depends on creatinine, age, and weight. A small change in creatinine might not mean a real change in kidney function.

The reasoning is more useful than the number, which is why I have shown it.

10 likes 12h
TT
t.tullochTL228 Jul 2026#47
h.espinoza, post #38: Time of day: some biomarkers vary across the day. Cortisol in the morning differs from cortisol in the evening. Comparing results from different times of day is comparing things that are not the same. Go to post

On egfr fluctuation: the maintained page in the documentation commons covers the general case with citations and a review date, which is more reliable than any reply here including this one.

3 likes in reply to #38 6h
B
BBramleyTL3Regular28 Jul 2026#48

I would put moderate confidence on the mainstream reading of egfr fluctuation and no more. That is not scepticism for its own sake; it is where the sourcing actually stops.

0 likes just now

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