PubMed Health⌕ Search

Biomedical subjects

T Helenius

Publications and source records attributed to T Helenius.

7 recordsLinked to original sources
PubMed1992

Fatty acid-induced increase in serum dialyzable free thyroxine after physical exercise: implication for nonthyroidal illness.

In 14 healthy males, prolonged running exercise resulted in a mean 25% increase in serum free T4 (FT4) concentration (P less than 0.001) which was significantly correlated (P less than 0.01-0.02) with an over 5-fold increase in the concentration of serum FFA and the FFA/albumin molar ratio. Hemoconcentration, as reflected in a mean 19% increase in serum albumin, caused an increase in serum T4-binding globulin and therefore also in serum total T4. As there was no change in the serum T4/T4-binding globulin molar ratio, the rise in serum FT4 was probably not caused, or only partly caused, by an exercise-induced shift of T4 from the extravascular to the intravascular compartment. Neither is it likely that the mean 41% increase in serum TSH observed after exercise, partly owing to hemoconcentration, was the reason for the increase in serum FT4 and T4 as there was no correlation between the increases in the TSH and thyroid hormone levels. Further support for the assumption that the elevation in serum FT4 after exercise was FFA-induced was provided by the observation that addition of 2.5 mmol/L oleic acid to normal serum in vitro resulted in a 33% increase in serum FT4 (P less than 0.001). There is an association between increased concentrations of serum FT4 and unsaturated FFA in patients with various nonthyroidal illnesses according to earlier observations, but it is unlikely, in the light of the present data from healthy subjects, that FFA are directly involved in raising the serum FT4 concentration in nonthyroidal illnesses patients unless the serum FFA concentration exceeds 2 mmol/L or the FFA/albumin molar ratio rises above 2.5.

Adult↗
PubMed1979

Abnormal thyroid function tests in devere non-thyroidal illness: diagnostic and pathophysiologic aspects.

In vitro thyroid function tests were studied in twenty-three patients with serious non-thyroidal illness. All had reduced protein binding of serum thyroxine (T4) and serum triiodothyronine (T3) as reflected in increased T4 and T3 uptake tests. The mean T4-binding prealbumin (TBPA) capacity and concentration were about one third the normal levels, whereas the decrease in R4-binding globulin (TBG) was much smaller. Increased serum free fatty acids and reverse T3 were frequently observed, but in vitro displacement of thyroid hormones from their binding sites was achieved only with much high concentrations of these compounds. Other still unrecognized substances significantly inhibiting binding of thyroid hormones might, however, occur in sera of severely ill patients. Evidence in favour of this possibility was the disproportionately high serum T4 by TBG-binding assay relative to T4 by radioimmunoassay. In most of the patients the dual-stage free T4 was elevated, whereas the single-stage free T4 index (CT4I) was within the reference interval. However, neither of these indices reflected the moderately increased dialysable free T4 concentration very accurately. The free T3 index was depressed in most of the patients, whereas the dialysable free T3 concentration was not affected. For practical purposes the combination of normal serum T4 and CT4I in a severely ill patient indicates absence of an associated thyrometabolic disorders.

Adult↗
PubMed1978

Thyroid function tests in patients on long-term treatment with various anticonvulsant drugs.

Thyroid function tests were studied in patients undergoing long-term treatment with various anticonvulsant drugs. Previous reports that diphenylhydantoin induces a decrease in the serum concentrations of total and free thyroxine (T4) and triiodothyronine (T3) without a change in the TSH concentration were confirmed. Diphenylhydantoin had no effect on reverse T3. Carbamazepine was also found to decrease serum T4, the free T4 index and T3 but, with the exception of T3, the decrease was smaller than that induced by diphenylhydantoin. Dipropylacetic acid did not influence the serum thyroid hormone concentrations, and neither did primidone. This demonstrates that the interaction between anticonvulsant drugs of different chemical structure and thyroid hormone metabolism is diverse. None of the drugs tested altered serum TSH or the T3 uptake test for the estimation of unsaturated thyroid hormone binding-capacity in serum. These two tests are considered diagnostically more dependable than the measurement of thyroid hormones in serum when diphenylhydantoin and carbamazepine are administered.

Adolescent↗
PubMed1978

Acute effects of alcohol on anterior pituitary secretion of the tropic hormones.

The plasma or serum concentrations of GH, TSH, LH, PRL, testosterone, cortisol, T4, and T3, and the values of the T3 uptake test were monitored in 12 healthy male volunteers for a period of 20 h after administration of one large dose of ethanol (1.5 g/kg BW). The effects of TRH and LRH on the secretion of TSH, PRL, and LH were studied in these subjects once during the period of acute alcohol intoxication (4 h after the start of drinking) and once during the hangover period (14 h after the start of drinking). Each subject served as his own control by drinking water only during another experimental session. Alcohol had no significant effect on basal concentrations of GH, TSH, LH, T4, T3, or testosterone. The concentration of cortisol in plasma was elevated during the whole 20-h period after ingestion of alcohol, as compared with the control values. Alcohol also did not significantly alter the effects of TRH and LRH on plasma TSH and LH levels at 4 and 14 h. During the hangover period, the PRL response to TRH was totally blocked, but during alcohol intoxication, there was a slight increase in the PRL response to TRH. The lack of response of PRL to TRH during the hangover suggests that withdrawal symptoms are associated with increased dopaminergic activity in the hypothalamus.

Adolescent↗
PubMed1976

Effect of fatty acids on thyroid function tests in vitro and in vivo.

Addition of long-chain fatty acids to serum increased thyroxine (T4), measured by a competitive protein binding assay, and triiodothyronine (T3) uptake by Sephadex or resin (T3U tests). This is compatible with the assumption that fatty acids compete with thyroxine for binding sites on T4-binding proteins. When equimolar concentrations of various saturated and unsaturated fatty acids were added to serum it was observed that the effectiveness in raising tests based on protein binding of thyroid hormones incrreased serum T3 determined by radioimmunoassay (RIA). T4(RIA) was not significantly influenced by either saturated or unsaturated fatty acids. Serum T4(CPB) rose during storage at 22degreesC and 37degreesC but was stable at 4degreesC and --20degreesC for periods up to two weeks. The proportional increase in T4(CPB) and free fatty acids (FFA) indicated that this phenomenon was due, at least partly, to the interference from FFA formed during storage of the serum. There was also a small, significant increase in T3U, T3(RIA) and CT4I (a free thyroxine estimate) after storage of serum at room temperature or higher for one to two weeks. Serum T4(RIA) did not alter during two weeks of storage. In five subjects with raised serum FFA after eating a fat meal followed by a heparin injection an increase in T4(CPB), T3U, T3(RIA) and CT4I that was proportional to the increase in FFA was observed. This effect on the thyroid tests was small until the increase in FFA concentration exceeded 2 mmol/l. T4(RIA) did not respond to the increase in FFA. In ten patients with raised levels of FFA due to uncontrolled diabetes T4(CPB), T4(RIA) and T3(RIA) decreased while T3U increased. These unexpected alterations were probably related to the severe, chronic illness in these patients. Increased FFA in vivo seem to be of little importance for the interpretation of thyroid tests in clinical practice.

Adult↗
PubMed1975

Comparison of serum free thyroxine indices and "corrected" thyroxine tests.

A dual competitive protein-binding assay for serum thyroxine (T4) is described. The assay is called the "corrected" T4 index and can be performed simultaneously with the determination of total T4. This method correlated significantly with the free T4 index and the effective T4 ratio. The "corrected" T4 index was compared for precision and diagnostic accuracy with the effective T4 ratio and two different free T4 indices. Improved modifications of the thyroxine and triiodothyronine Sephadex uptake tests, used for calculation of the free T4 indices, are also reported. In spite of better precision, the "corrected" T4 index and effective T4 ratio gave twice as many incorect classifications of both hyper- and hypothyroidism as the free T4 indices. Previous reports on the effective T4 ratio and other basically similar tests might give an overly optimistic view of what can be expected in routine clinical practice. The free T4 index, which is a good estimate of the free T4 concentration, may still be the thyroid function test of choice when serum T4 and clinical impression are not in conformity.

Adult↗