Figure 1c. Temperature before and after T3 administration (T3 given at time 0 hours)
It appears that the liothyronine could have advanced the phase of circadian temperature. However, since the study had no controls, it is impossible to confirm this hypothesis.
Half-life22.04 hours
It appears they are calculating based on total T3 rather than added T3. Assuming that the conversion of T4 to T3 remains constant, the half life of the liothyronine dose towards baseline is less than 10 hours (I'd estimate 5-7 hours). Given that this is short compared to other studies, it is likely that the conversion was slowed by the high thyroid status.
The present study shows that daily administration of T3 was associated with peaks and troughs in T3 concentration. However, TSH and fT4 remained steady on both a weekly and hourly basis.
I'm not sure what they mean here by 'weekly basis' Levels did change on a weekly basis. Hourly, on the other hand, they did not change.
I'm surprised that TSH didn't drop a few hours after liothyronine administration. I see two possible reasons; either TSH is a measure of average thyroid activity, or T3 has slow/delayed effects. If the latter is the case, then there doesn't seem to be any reason to spread out liothyronine doses.
(A)–(C) Changes in markers of thyroid status over the course of the study (mean ± standard error). (D) Changes in treatment preference.
Looks like preference for T3 increased as the number of hyperthyroid symptoms increased. It would be interesting to know if those are the same patients.
In an observational study of 14 patients, no subjects developed any cardiac or skeletal disease after receiving doses from 25- to 150mcg over a two-year period.41
Note that the high dose was because they were increasing the dose based on symptoms. That is to say, as the thyroid gland produced less thyroid hormone, they increased liothyronine dose to compensate.
SBP, DBP, RR, and weight did not change following T3 administration
Liothyronine does not raise blood pressure despite the rise in heart rate. The reason that respiratory rate (RR) was not changed may be because the increased cardiac output compensates for the increased oxygen demand.
The peak T3 concentration after LT3 administration during week 6 was 292.8 ± 152.3 ng/dL, rising from a baseline value of 96.1 ± 7.6 ng/dL
The T3 half-life, therefore, is only 14.25 hours (14 hours and 15 minutes). I calculated this based on taking the peak value and comparing it to the baseline value 22 hours later.
Since they've been on the same dose during this study period, the baseline value is what's left from yesterday's peak, and can be assumed to be tomorrows trough. Since the drug took 2 hours to peak, there are 22 hours remaining to reach trough/baseline values.
AbstractHigh dose thyroid hormone has been in use since the 1930s for the treatment of affective disorders. Despite numerous papers showing benefit, the lack of negative trials and its inclusion in multiple treatment guidelines, high dose thyroid has yet to find wide spread use. The major objection to the use of high dose thyroid is the myth that it causes osteoporosis. This paper reviews the literature surrounding the use of high dose thyroid, both in endocrinology and in psychiatry. High dose thyroid does not appear to be a significant risk factor for osteoporosis while other widely employed psychiatric medications do pose a risk. Psychiatrists are uniquely qualified to do the risk-benefit analyses of high dose thyroid for the treatment of the bipolar I, bipolar II and bipolar NOS. Other specialties do not have the requisite knowledge of the risks of alterative medications or of the mortality and morbidity of the bipolar disorders to do a full risk benefit analysis.
This is all very interesting. It is also true that, in the treatment of depression, there is a relatively low dropout rate due to side effects from treatment with T3 (liothyronine).
liothyronine (T3) augmentation in the treatment of depression
Studies reported by Nicoloff and colleagues in 1972 calculated a half-life of T3 that varied with thyroid status (8). The mean half-life was 0.63 days in 7 hyperthyroid patients, 1.0 day in 8 euthyroid individuals, and 1.38 days in 9 hypothyroid patients.
There was a boy who was born with congenital hypothyroidism and was raised on traditional T3 (Cytomel). He was never treated with a T4-containing medicine, and so essentially never had a molecule of T4 in his body. By age 26 he had developed normally with no problems.
This is precisely the type of information I was looking for. Wikipedia implied T4 should be taken with long-term T3, but the reasoning was poorly explained. However, I'd like a more official source for this case report.
This case would also express no rT3 (reverse-T3). Thus, it appears that neither T4 nor rT3 serve any vital functions.