Serum free triiodothyronine

Thompson JE, Baird SG, Thomson JA. Effect of i.v. heparin on serum free triiodothyronine levels. Br J Qin Pharmacol 1977 4 701. 

A 67-year-old man took amiodarone 200 mg/day for 20 months, after which it was withdrawn 8 months later his serum TSH was suppressed and the free thyroxine and free triiodothyronine were both raised there were no thyroid antibodies and an ultrasound scan showed a diffuse goiter with a nodule in the right lobe and reduced iodine uptake (45). Histological examination of the nodule showed a papillary cancer. 

After 6 months of treatment, 12% of patients with chronic hepatitis C had thyroid disorders, compared with 3% of patients with chronic hepatitis B. This study also suggested a possible relation between low free triiodothyronine serum concentrations before treatment and the subsequent occurrence of thyroid dysfunction. After a follow-up of 6 months after the end of interferon alfa treatment, 60% of affected patients with chronic hepatitis C still had persistent thyroid dysfunction all had been positive for thyroid peroxidase antibodies before treatment. Long-term surveillance is therefore needed in these patients. 

Artefactual increases of as much as 50% in total thyroxine, estimated by a competitive protein-binding assay, and of as much as 30% in triiodothyronine resin uptake are probably due to rapid and continuing lipolytic hydrolysis of triglycerides after blood has been drawn (126). Thyroid function tests should therefore always be performed on blood samples taken before (or a sufficient time after) heparin treatment (127). An increase in serum-free thyroxine concentrations has also been reported after low molecular weight heparin, by up to 171% in specimens taken 2-6 hours after injection. When specimens were obtained 10 hours after injection, the effects were smaller, but with concentrations still up to 40% above normal the results can still cause errors of interpretation (128). 

After 6 months of treatment, 12% of patients with chronic hepatitis C had thyroid disorders, compared with 3% of patients with chronic hepatitis B. This study also suggested a possible relation between low free triiodothyronine serum concentrations before treatment and the... 

Metallic Mercury. A 13-year-old boy exposed to mercury vapors for 2 weeks developed a thyroid enlargement with elevated triiodothyronine, and thyroxine and low thyroid-stimulating hormone levels (Karpathios et al. 1991). Serum-free thyroxine (T4) and the ratio of free thyroxine to free 3,5,3 -triiodo-... 

Immunoassay kits using luminol and arylacridinium ester labels have been developed by nine companies for a variety of thyroid, steroid and pituitary hormones, viruses, digoxin, and creatine kinase. One assay for total and free thyroxin has detection limits of 20 pM in serum, while another for total and free triiodothyronine has a 3-pM detection limit in serum. These analytes are used as clinical indicators of thyroid gland malfunction. While research has shown that... 

Peterson B, Hanson R, Giese R, Karger B. Picogram analysis of free triiodothyronine and free thyroxine in serum by equilibrium dialysis and electron capture gas chromatography. J Chromatogr 1976 126 ... 

Sophianopoulos JA, Jerkunica I, Sgoutas DS. A rapid ultrafiltration method for the measurement of free thyroxine (FT4) or free triiodothyronine (FT3) in serum. Clin Chem 1979 25 1080-1. 

After treatment is initiated, patients should be examined and thyroid function tests (serum-free thyroxine index and total triiodothyronine concentrations) measured every 2 to 4 months. Once euthyroidism is established, follow-up every 4 to 6 months is reasonable. 

Figure 106.1 Evaluation of patients with abnormal serum thyrotropin (TSH) oonoentrations. Schematic aigorithm for the evaiuation of a patient with abnormal thyrotropin (TSH) with an indication of the most oommon diagnoses in the absence of nonthyroidai iiinesses and drugs affecting thyroid hormone concentrations. Abbreviations t, high low n, normal FT4, free thyroxine FT3, free triiodothyronine L-T4, levothyroxine.

L3. Larsen, P. R., Salicylate-induced increases in free triiodothyronine in human serum Evidence of inhibition of triiodothyronine binding to thyroxine-binding globulin and thyroxine-binding prealbumin. /. Clin. Invest. 51, 1125-1134... 

J. Ortiz-Caro, B. Yusta, F. Montiel, A. Villa, A. Aranda and A. Pascual, Identification and characterization of nuclear T3 receptors in cells of glial and neuronal origin. Endocrinology 119 2163 (I986). J. Puymirat and A. Faivre-Bauman, Evolution of triiodothyronine nuclear binding sites in hypothalamic serum-free cultures evidence for their presence in neurons and astrocytes, Neurosci. Lett. 68 299... 

Serum free thyroxine (FT ) and free triiodothyronine (FT ) were directly measured by radioramunoassay in serum dialysates with normal ranges of 20-40 pg/ml and 4-8 pg/ml respectively. 

Picogram Analysis of Free Triiodothyronine and Free Thyroxine Hormones in Serum by Equilibrium Dialysis and Electron Capture Gas Chromatography... 

A 41-year-old man who habitually inhaled cocaine developed severe fatigue, cold intolerance, anorexia, and weight loss of 20 kg over 6 months. He had low serum concentrations of TSH, free thyroxine, and free triiodothyronine, FSH, LH, ACTH, cortisol, prolactin, and testosterone. MRI and CT scans showed a normal sized pituitary gland within a dense, edematous, contrast-enhancing mass. The nasal septum was destroyed, and there were no conchae and severely eroded sinus walls. 

Thyroid effect. Goffee oil, administered orally to 11 healthy normolipemic volunteers at a dose of 2 g/day for 3 weeks, produced no effect on serum total and free thyroxine, triiodothyronine, and thyroid-stimulating hormone... 

There was a modest rise in serum TSH concentration when rifampicin was given to a patient previously stabilized on thyroxine replacement (87). Rifampicin is believed to increase the metabolic clearance of both thyroxine and the inactive compound reverse triiodothyronine and in healthy volunteers it reduces circulating concentrations of total and free thyroxine, although in subjects without thyroid disease it has no effect on serum TSH (86). 

Despite the fact that she was clinically euthyroid, the authors suggested that this patient had amiodarone-induced hyperthyroidism. However, amiodarone inhibits the peripheral conversion of thyroxine to triiodothyronine it can therefore increase the serum thyroxine and suppress the serum TSH, as in this case. On the other hand, the reduced uptake by the thyroid gland is consistent with type 2 amiodarone-induced hyperthyroidism. The authors did not report the serum concentrations of free thyroxine and triiodothyronine. 

In five patients who presented in Tasmania during 1 year, all of whom were taking amiodarone 200 mg/day, serum TSH was undetectable and the free thyroxine and triiodothyronine concentrations were raised (46). In one case there was a low titer of TSH receptor antibodies and in another a high titer of antithyroid peroxidase antibodies. In all cases the hyperthyroidism was severe and occurred after at least 2 years of treatment with amiodarone. In one of two patients in whom it was measured the serum concentration of interleukin-6 was raised, as has been previously shown (SEDA-19, 193). In two cases the hyperthyroidism was refractory to treatment with propylthiouracil, lithium, and dexamethasone in these cases thyroidectomy was required. Two patients responded to propylthiouracil, lithium, and dexamethasone, and one responded to carbimazole. 

Sojka J E, Johnson M A, Bottoms G D 1993 Serum triiodothyronine, total thyroxine, and free thyroxine concentrations in horses. American Journal of Veterinary Research 54 52-55 Medical Economics Staff, PDR Staff and Physicians 2002 Physician s Desk Reference 2003, 57th edn. Thompson Healthcare, Montrale, NJ, pp. 569-571 Williams P D 1995 Equine Cushing s syndrome ... 

---