Protein-bound iodine

Systemic iodine absorption can occur after intravaginal administration of povidone-iodine (11). There were increases in serum iodine, protein-bound iodine, and inorganic iodine, but not serum thyroxine, after a 2-minute vaginal administration of povidone-iodine in non-preg-nant women (12). 

Body fluids are analyzed for T and T by a variety of radioimmunoassay procedures (31) (see Immunoassays). The important clinical parameter for estimating thyroid function, the protein-bound iodine (PBI), is measured as described in treatises of clinical chemistry. High performance Hquid chromatographic (hplc) methods have replaced dc (32,33). 

IPPB intermittent positive pressure breathing PBI protein-bound iodine... 

Sanz, M C. Brechbuhler, T and Green, I J The ultramicro-determination of total and protein-bound iodine. Clin Chem (1956), 1, 570 - 576 ... 

Peptides in Human Urine (Skarzynski and Samecka-Keller), 5, 107 Protein Bound Iodine (Chaney), I, 82 Radioactive Iodine-131 in the Diagnosis of Hyperthyroidism, Blood Plasma Levels of (Silver), 1, 111 Transaminase Activities of Serum and Body Fluids, the Clinical Significance of Alterations in (Wroblew-ski), 1, 314... 

Oral contraceptives have also been reported to produce increases in sulfobromophthalein retention and other liver function tests, as well as in prothrombin time, clotting factors VII, VIII, IX, serum thyroxine, and protein-bound iodine (B8). In a group of 48 women the mean cholesterol value was 206 41 mg/100 ml while they were receiving a variety of oral contraceptives and 179 28 mg/100 ml when they were not receiving the drugs (W19). 

Oral contraceptives have their most significant effect on endocrine parameters. Blood cortisol, thyroxine, protein-bound iodine, T3 uptake, and urinary free cortisol are elevated. Urinary 17,21-dihydroxy steroids, 17-ketosteroids, and estrogens are decreased. There is no effect on urinary catecholamines or VMA (Table 10) (LIO). The effect of thyroid functions tests is due to the administered hormone stimulating an increase in the production of thyroid-binding globulin which in turn binds 1-thyroxine. The lowering of free thyroxine stimulates the anterior pituitary to produce thyrotropin, which in turn stimulates the thyroid to produce more thyroxine. Since the additional thyroxine is bound to the extra protein, there is an equilibrium and the patient remains clinically euthyroid, but the protein-bound iodine and the thyroxine are elevated. 

Al. Acland, J. D., The interpretation of the serum protein-bound iodine A review. J. Clin. Pathol. 24, 187-218 (1971). 

B18. Boklan, B. F., and Rooney, J., Effect of intramuscularly administered mercury on determination of protein-bound iodine. N.Y. State J. Med. 70, 2806-2808 (1970). 

D2. Davis, P. J., Factors affecting the determination of the serum protein-bound iodine. Amer. J. Med. 40, 918-935 (1966). 

Schultz, A. L., Influence of drugs on thyroid P uptake and serum chemical protein-bound iodine. Postgrad. Med. 31, A34-A39 (1962). 

Phenothiazines may increase serum cholesterol, spinal fluid protein, and urinary urobilinogen levels decrease protein bound iodine yield false-positive urine bilirubin tests interfere with urinary ketone and steroid determinations. 

Endocrine effects Salicylates decrease the plasma protein bound iodine due to displacement of thyroxine from prealbumin and stimulation of central sympathetic centre causes release of adrenaline from the adrenal medulla. 

Oral contraceptives can cause an increase in total thyroxine (163) and a fall in the percentage of free thyroxine (164). The uptake of radioactive iodine in the thyroid is usually normal total uptake of radioactive iodine may be reduced (164). The effect of progestogens on thyroxinebinding globulin may possibly counteract the estrogenic action. The net result will be a rise in protein-bound iodine and a fall in resin triiodothyronine uptake (165). It has been suggested that oral contraceptives may actually have some protective effect against thyroid disease. 

Estimation of protein-bound iodine and tracer studies for the estimation of thyroid function are interfered with by the use of iodine-containing compounds (73). 

Occasional increases in protein-bound iodine have occurred (593). 

The iodinated thyroglobulin is stored as a colloid in thyroidal follicular cells, and T3 and T4 are liberated from it by proteolysis as required. It is estimated that ca 90 Jig of T4 and 6 Jig of T3 are secreted daily by the thyroid gland, giving mean plasma concentrations of 80 and 2 lg/L, respectively, of which only 0.03 and 0.3% are in the free form, ie, not protein bound (21). The half-life of T4 in the body is long (6—7 d) (2) that of T3 is somewhat shorter... 

It would appear that there is a sudden increase in thyroid activity in terms of available or free hormone and an alteration in thyroxine-binding protein which starts probably during surgery and anesthesia and is associated with an increased peripheral utilization of thyroid hormone. Although changes in protein-bound iodine (FBI) and TSH concentrations are not necessarily related to secretion rates, the exact extent of any increase in secretion of thyroid hormone secretion remains uncertain. 

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