Latest research on Levothyroxine

The major hormone derived from the thyroid gland. Thyroxine is synthesized via the iodination of tyrosines (monoiodotyrosine) and the coupling of iodotyrosines (diiodotyrosine) in the thyroglobulin. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroxine is peripherally deiodinated to form triiodothyronine which exerts a broad spectrum of stimulatory effects on cell metabolism. [PubChem]

Levothyroxine dosage

The Thyroid is absent, the hormone levels are low, the physician prescribes a dose of Levothyroxine to replace what the body would otherwise manufacture, and that resolves the problem. [source, 2016]
The adequacy of L-T4 replacement dose depends, among other things, on the patient’s age, sex, menopausal status, and body weight. [source, 2016]
There is no indication for routine measurement of free T4 concentrations in patients on L-T4 when TSH is being monitored, unless the physician is concerned that the patient is not compliant with the prescribed dose. [source, 2016]
If T4 measurements are drawn, it should be after an overnight fast and before the daily dose of L-T4.14 [source, 2016]
Suppression of TSH, using supraphysiological doses of L-T4, is used commonly to treat patients with Thyroid cancer in an effort to decrease the risk of recurrence.2–7 [source, 2016]
In women receiving L-T4 for replacement alone, the dose should be increased by 30% as soon as pregnancy is confirmed. [source, 2016]
The pre-pregnancy dose of L-T4 should be immediately resumed after delivery.14,38 [source, 2016]
One daily dose of L-T4 accounts for 14% of the total weekly dose. [source, 2016]
Therefore a missed dose of L-T4 may affect free T4 and TSH levels over several weeks due to the long half-life of L-T4. [source, 2016]
If efforts to encourage regular daily consumption of L-T4 are unsuccessful, alternative options for medication delivery include twice weekly or once weekly dosage. [source, 2016]