Enda en artikkel om døgnvariasjoner i TSH, samt at denne studien mener å vise at forsinkelsen i reaksjonen i ft3 er ca 90min.

Results: Of the individuals, 100% showed a sinusoidal signal in TSH, for FT4 76%, and for FT3 86% (P < 0.05). For FT4 and FT3, the amplitude was low. For TSH the acrophase occurred at a clock time of 0240 h, and for FT3 approximately 90 minutes later at 0404 h. The group cosinor model predicts that TSH hormone levels remain above the mesor between 2020 and 0820 h, and for FT3 from 2200–1000 h. Cross correlation of FT3 with TSH showed that the peak correlation occurred with a delay of 0.5–2.5 h. When time-adjusted profiles of TSH and FT3 were compared, there was a strong correlation between FT3 and TSH levels ( = 0.80; P < 0.0001). In contrast, cross correlation revealed no temporal relationship between FT4 and TSH.
(Min utheving.)

Conclusions: FT3 shows a circadian rhythm with a periodicity that lags behind TSH, suggesting that the periodic rhythm of FT3 is due to the proportion of T3 derived from the thyroid. Optimizing thyroid hormone replacement may need to take these rhythms into account.
http://jcem.endojournals.org/cgi/content/full/93/6/2300

Om ikke annet så er dette en VELDIG god grunn til å insistere på å bli styrt etter ft4 og ikke TSH....

Studien nevner også kombinasjonsbehandling og lenker til andre studier vedrørende dette.
After the first publication that a combination replacement therapy of T4 and T3 may improve quality of life for hypothyroid patients (13), there has been considerable debate as to the actual benefits. Despite a large number of studies, there is no conclusive evidence that combination therapy with T4 and T3 improves efficacy of therapy or health-related quality of life (14). A major criticism of most studies is the lack of physiological combination therapies. It has been proposed that: "the ideal substitution therapy for hypothyroidism might be a combination of T4 and T3 in a carefully determined ratio and in a form in which T3 is slowly absorbed in a time-release form" (15). In response to this, a slow-release formulation of T3 has been developed, and initial proof of principle studies in humans suggests a good pharmacokinetic profile (16). In view of this debate and potential therapeutic developments, we felt it was important to establish the exact rhythms of FT4 and FT3 in the normal population. To do this we have studied FT4 and FT3 levels in a group of normal controls in which TSH levels had previously been measured and reported (17).