Thanks for your input, hormone meds are definetly a mystery.
I don't have that issue personally but if my breathing issues worsen (one of my hypothyroid symptoms) I take thyroxine immediately and maybe an hour or two later this symptom improves.
Excerpts from the book: Thyroid Diseases: Clinical Fundamentals and Therapy by Fabrizio Monaco, Maria A. Satta, Brahm Shapiro, Luigi Troncone...
"There is some differences in the rate of absorption between animal and synthetic preparations. After a single oral dose of synthetic L-T4, the absorption is approximately 70 - 80%, 20 - 30% being recovered in the stool. It is absorbed rapidly, mainly in the distal small bowel, reaching maximum plasma levels in 2 to 4 hours."
"Variability of absorption also occurs with desiccated thyroid, dependent on proteolytic enzymes of the gastrointestinal tract. Since desiccated thyroid and thyroglobulin preparations contains T4 and T3 incorporated into thyroglobulin, to release thyroid hormone the crude preparations must be hydrolyzed by gastrointestinal proteolytic enzymes, which indirectly influence the absorption of T4 and T3."