I am looking for solid reference to infer mean (human) plasma cortisol concentration of a time unit (e.g. 12hrs) from measured urinary cortisol concentrations (mean cortisol concentration of a 12hr unit, normalised to creatinine concentration). I need it to use a mathematical cortisol model, of which most published ones only use plasma concentrations, but I only have urinary measures.
Currently I am brute-forcing papers from 50-60 years ago, which doesn't quite help me. Is there anything more recent, or a physiology book that gives me more information about the topic?
Sofar I found that "Urinary free cortisol excretion increases directly in proportion to the plasma unbound cortisol level (Beisel et al, 1964) and provides an integrated measure of plasma free cortisol over time (Burke & Roulet, 1970). (from Carroll76)
Thank you very much.
Sometimes one can find more recent and more relevant research by checking the papers citing an old paper related to the topic (and possibly repeating the search starting from the newly found papers). I have no experience with the subject though.
I'm not sure that you can, with any meaningful accuracy. There are several difficulties, the most problematic being that cortisol has a diurnal pattern of expression, and this pattern may be different in different biofluids overall, and more or less discordant as concentrations increase or decrease.
In saying that, here are some references which might be useful to you - serum and plasma levels are likely to be very similar so you might have better luck with that literature.
DOI:10.1016/s1440-2440(02)80031-7
DOI: 10.1080/036107399244075
Article Plasma, salivary and urinary cortisol levels following physi...
I can’t answer you, because i dont have domain.
Thank you .
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