Relationships Between Blood Thyrotrophin Level, Protein Bound Iodine and Free Thyroxine Concentration in Man Under Normal Physiological Conditions

Abstract

A study of the thyroid-pituitary interrelationships in normal healthy subjects is carried out by measurements of plasma thyrotrophin (TSH), by a radioimmunoassay, protein bound iodine (PBI) and free thyroxine (T4). It has been found that: – PBI and TSH significantly increase with age, which probably results from a peripheral hypometabolism, in spite of a normal free T4 concentration; – there are circadian variations of free T4 accompanied by a non significant inverse relationship of the plasma TSH level; – no important changes occur during the normal menstrual cycles but there is a significant increase in both PBI and TSH during pregnancy. The secretion of pituitary TSH seems to be finely regulated not only by the free plasma thyroxine concentration but also by the rate of metabolism of the thyroid hormones in the cell.

A new method for the measurement of thyroidal iodine release in man

“…These values closely correspond to our mean peak values of 4:00 a.m. and the nadir values of 5:00 p.m. In addition, diurnal variations in pituitary or serum TSH levels have been reported to occur in laboratory animals (7,(28)(29)(30).…”

“…Utiger, employing an immunoassay for human plasma TSH, was unable to detect any diurnal variation in plasma TSH values in normal subjects (27). In contrast, Lemarchand-Beraud and Vannotti, using a bovine TSH assay system which cross-reacted with human TSH, found a diurnal trend in plasma TSH values (28). They observed the peak TSH values to occur at 4:00 a.m. and the nadir values at 4:00 p.m. daily.…”

The role of glucocorticoids in the regulation of thyroid function in man

“…The preoperative release pattern was similar to that observed in normal subjects as illustrated in Fig. 1 11.2 mug/ml preoperatively to 1.0 myg/ml postoperatively. Urinary ketogenic steroid excretion values fell to 3.9 mg/24 hr and were 4.7 mg/24 hr after metapyrone administration ,and 24-hr urinary gonadotropin levels became undetectable.…”

Plasma Thyrotropin Levels in Severe Infantile Malnutrition

“…The cross-reaction of this bovine antiserum with human TSH had been previously dem onstrated [13,33], and all the results obtained with this assay were in agreement with thyroid physiology [32]. Unfortunately, in 1968-1969, when the human TSH radio immunoassay was also developed in our laboratory, no more plasmas from the children were available for measurement with the homologous system.…”

“…As this study was started in 1967, before human TSH was available, plasma TSH was measured by a heterologous radioimmunoassay, previously described [13], using highly purified bovine TSH as labelled hormone and the bovine TSH-USP reference as standard.…”