A Radioimmunoassay for 3,3′-L-Diiodothyronine (3,3′T₂)

3,3′-Diiodothyronine Production, a Major Pathway of Peripheral Iodothyronine Metabolism in Man

“…The presence of 3,3'-T2 in normal whole serum at a slightly higher concentration (17.0±+1.0 ng/100 ml) measured by radioimmunoassay has also been reported by Burman et al. (7).…”

“…(25), who demonstrated that 3,3'-T2 comprised <2% of the total 13'I in the thyroids of severely iodinedeficient rats and even less in the iodine-replete animal. In a recent report Burman et al (7) found a 3,3'-T2 concentration of 0.4+0.03 ,ug/g in normal thyroid tissue and a lack of a serum 3,3'-T2 response secondary to thyrotropin-releasing hormone stimulation, findings indicative of a minimal rate of thyroidal secretion. That the thyroid gland is not a major source of circulating 3,3'-T2 is confirmed by the similar 3,3'-T2 PR in the euthyroid control group and in the athyreotic subjects in whom the only source of 3,3'-T2 was exogenous T4.…”

“…Three groups have described radioimmunoassays for 3,3'-T2 in normal human serum, although the reported levels do not agree (6)(7)(8). No quantitative estimates have been made, however, of the turnover of 3,3'-T2 in humans.…”

Hepatic extraction and renal production of 3,3'-diiodothyronine and 3',5'-diiodothyronine in man.

“…Receivedfor publication 21 April 1980 and in revisedform 8 July 1980. 1Abbreviations used in this paper: 3,3'-T2, 3,3'-diiodothyronine; 3',5'-T2, 3',5'-diiodothyronine; 3'-T1, 3'-monoiodothynormal components of human serum (1)(2)(3)(4)(5)(6). They are produced predominantly by extrathyroidal degradation of thyroxine (T4) (5), which proceeds by serial monodeiodination until all the iodine atoms have been removed (7).…”

Metabolism of 3,3'-diiodothyronine and 3'-monoiodothyronine, and effect of potassium cyanide and dinitrophenol on glucuronidation of thyroxine in cultured rat hepatoma cells.

“…In fact, 3, 3'-T2 was detected in the rat kidney after injection of the thyroid hormones (Roche et al, 1956;Roche et al, 1959) and in serum (Wu et al, 1976;Burman et al, 1977;Burgar and Sakoloff, 1977;Gavin et al, 1978). Furthermore, 3, 3' -T2 conjugates were identified in bile, urine or plasma (Flock et al, 1960;1963).…”