We developed and validated a non-invasive thyroid hormone measure in feces of a diverse array of birds and mammals. An I(131) radiolabel ingestion study in domestic dogs coupled with High Pressure Liquid Chromatography (HPLC) analysis, showed that peak excretion in feces occurred at 24-48h post-ingestion, with I(131)-labelled thyroid hormone metabolites excreted primarily as triiodothyronine (T...

Thyroid hormone production is regulated via pituitary thyrotropin (TSH) modulation of thyroxine (T4) prohormone secretion by the thyroid gland and regulation of active triiodothyronine (T3) production in peripheral tissues via metabolic events influencing activities of the iodothyronine monodeiodinase enzyme systems. Control at both levels is developmentally regulated and modified in serious no...

We studied the effect of thyroid hormone administration on responsivity of murine thyroid to exogenous thyrotropin (TSH) in order to explore the possibility that the thyroid gland might be directly inhibited by its own hormones. In the rat both L-thyroxine (T4) and 3,5,3'-L-triiodothyronine (T3) pretreatment inhibited TSH-induced thyroidal ornithine decarboxylase (ODC) activity in vivo in a dos...

The thyroid hormones (3,5,3',5'-tetraiodo-L-thyronine [L-T4]' and 3,5,3'triiodo-L-thyronine [L-T3]) have marked effects on the growth, development, and metabolic function of virtually all organ systems and tissues ofhuman beings and other higher organisms (1-3). L-T4 was one of the first hormones to be isolated and its structure determined (4-6). Several decades later L-T3 was identified in the...

In a seemingly wasteful fashion, the thyroid gland focuses its effort into secreting an inactive version of thyroid hormone T4. In fact, a hormone, from the Greek word for impulse, is a biologically active molecule, so in the case of thyroid hormone, the actual active hormone is that of the triply iodinated derivative, T3. To successfully produce T3, the human thyroid processes about 1000 nmol ...

The degree to which thyroid functions are affected by non-thyroid illness and an assessment of its correlation with mortality was evaluated. Thirty infants (20 M, 10 F) with a mean age of 433 +/- 3.28 months (+/- 1 SD), with severe acute systemic illness and 30 healthy controls, age and sex matched, were studied for total serum T3, T4 and TSH levels at admission and recovery or before death. Se...

A stimulatory effect on bone marrow cellularity was observed in normal and nephrectomized rats continuously infused with T3 and T4. Results of bone marrow studies are expressed in absolute numbers of total nucleated erythroid cells per milligram of femoral marrow at the beginning and after 8 hr of continuous intravenous infusions. Administration of T3 and T4 to nephrectomized rats produced a ma...

Recent studies indicate that co-planar 3,3',4,4',5-pentachlorobiphenyl (PCB) congeners or their metabolites may disrupt thyroid function in fishes. Although co-planar PCB have been detected at microgram per kilogram levels in fish from contaminated areas, few studies have examined mechanisms whereby, co-planar PCBs may alter thyroid function in fish. We treated immature lake trout by intraperit...