Serum Free Triiodothyronine Levels Research Articles

Thyroid Hormone Replacement Therapy in Primary Hypothyroidism: A Randomized Trial Comparing l-Thyroxine plus Liothyronine with l-Thyroxine Alone

Substituting part of the dose of l-thyroxine with small but supraphysiologic doses of liothyronine in hypothyroid patients has yielded conflicting results. To evaluate combinations of L-thyroxine plus liothyronine in hypothyroid patients that match the proportions present in normal secretions of the human thyroid gland. Randomized, double-blind, crossover trial. Academic research hospital. 28 women with overt primary hypothyroidism. Crossover trial comparing treatment with l-thyroxine, 100 microg/d (standard treatment), versus treatment with L-thyroxine, 75 microg/d, plus liothyronine, 5 microg/d (combination treatment), for 8-week periods. All patients also received L-thyroxine, 87.5 microg/d, plus liothyronine, 7.5 microg/d (add-on combination treatment), for a final 8-week add-on period. Primary outcomes included serum thyroid hormone levels, results of quality-of-life and psychometric tests, and patients' preference. Multiple biological thyroid hormone end points were studied as secondary outcomes. Compared with standard treatment, combination treatment led to lower free thyroxine levels (decrease, 3.9 pmol/L [95% CI, 2.5 to 5.3 pmol/L]), slightly higher serum levels of thyroid-stimulating hormone (increase, 0.62 mU/L [CI, 0.01 to 1.23 mU/L]), and unchanged free triiodothyronine levels. No improvement was observed in the other primary and secondary end points after combination treatment, with the exception of the Digit Span Test, in which the mean backward score and the mean total score increased slightly (0.6 digit [CI, 0.1 to 1.0 digit] and 0.8 digit [CI, 0.2 to 1.4 digits], respectively). The add-on combination treatment resulted in overreplacement. Levels of thyroid-stimulating hormone decreased by 0.85 mU/L (CI, 0.27 to 1.43 mU/L) and serum free triiodothyronine levels increased by 0.8 pmol/L (CI, 0.1 to 1.5 pmol/L) compared with standard treatment; 10 patients had levels of thyroid-stimulating hormone that were below the normal range. Twelve patients preferred combination treatment, 6 patients preferred the add-on combination treatment, 2 patients preferred standard treatment, and 6 patients had no preference (P = 0.015). Treatment with L-thyroxine, 87.5 microg/d, plus liothyronine, 7.5 microg/d, was an add-on regimen and was not randomized. Physiologic combinations of L-thyroxine plus liothyronine do not offer any objective advantage over l-thyroxine alone, yet patients prefer combination treatment.

Antithyroid Antibody Levels in Patients with Breast Cancer

Breast cancer is a hormone-dependent neoplasm. Conflicting results regarding the clinical correlation between breast cancer and thyroid diseases have been reported. The aim of this study was to determine the goiter prevalence, thyroid hormones and antithyroid antibody levels in patients with breast cancer. For this purpose, thyroid ultrasonography was performed and serum levels of free triiodothyronine (FT3 ), free thyroxine (FT4 ), thyroid-stimulating hormone (TSH), anti-thyroid peroxidase antibodies (anti-TPO ab) and anti-thyroglobulin antibodies (anti-TG ab) were determined in 50 operable breast cancer patients at the time of diagnosis and 30 healthy individuals as control group. Goiter prevalence was found to be significantly higher in the study group (50% vs 10%). FT3 , FT4 , and TSH levels of patients were not different compared to controls, whereas anti-TPO ab and anti-TG ab levels were significantly higher in patients than in the control group. In conclusion, goiter prevalence and thyroid antibody levels were found to be increased in breast cancer patients and thyroid functions should be monitored.

Thyroid function is associated with presence and severity of coronary atherosclerosis.

Overt hypothyroidism has been found to be associated with cardiovascular disease. Moreover, subclinical hypothyroidism is a strong indicator of risk for aortic atherosclerosis and myocardial infarction. We hypothesized that variation of thyroid function within the normal range may influence the presence and severity of coronary atherosclerosis. We studied a total of 100 consecutive men and women (59 men, 41 women, age 63.7 +/- 11.0 years) who underwent coronary angiography. Blood was tested for serum thyrotropin concentrations and for free tri-iodothyronine and free thyroxine concentrations. In addition to the assessment of thyroid function, conventional risk factors for coronary artery disease (CAD), clinical characteristics, serum lipid levels, fasting total homocysteine, and angiographic results of coronary artery assessment were obtained. Two experienced cardiologists blinded to clinical and laboratory data reviewed the cinefilms. The severity of CAD was scored as 0 for those with smooth normal epicardial coronary arteries, 0.5 for plaquing (< 50% diameter stenosis), and 1, 2, or 3 for those with single-, double-, or triple-vessel epicardial coronary artery stenosis of > 50%, respectively. The severity of CAD was scored as 0, 0.5, 1, 2, and 3 in 14, 26, 25, 22, and 13 patients, respectively. Higher levels of serum-free thyroid hormone concentrations were associated with decreased severity of coronary atherosclerosis. Serum-free tri-iodothyronine was 2.99 +/- 0.33 pg/ml in patients with a CAD severity score of 0 to 1 and 2.74 +/- 0.49 pg/ml in patients with CAD severity scores of 2 and 3 (p < 0.01). Moreover, serum-free thyroxine concentrations showed a trend toward higher levels in patients with CAD severity score 0 to 1 compared with patients with CAD severity scores 2 and 3 (11.65 +/- 1.87 pg/ml vs. 10.9 +/- 2.3 pg/ml; p = 0.09). Higher levels of serum thyrotropin concentrations were associated with increased severity of coronary atherosclerosis (1.37 +/- 1.02 mU/l vs. 1.98 +/- 2.13 mU/l in patients with CAD severity score 0 to 1 versus CAD severity scores 2 and 3; p = 0.049). When grouped into three subsets according to their serum free tri-iodothyronine levels (< 2.79, 2.8 to 3.09, and +/- 3.1 pg/ml), the prevalence of CAD scores 2 and 3 was significantly higher in the subset of patients with low serum free tri-iodothyronine levels (48.5%) than in the subsets of patients with medium or high tri-iodothyronine concentrations (32.25 and 25%, respectively, p for trend < 0.05). These data in patients referred for coronary angiography suggest that variation of thyroid function within the statistical normal range may influence the presence and severity of coronary atherosclerosis.

The Nocturnal Serum Thyrotropin Surge Is Inhibited in Patients with Adrenal Incidentaloma

BackgroundAlterations in hypothalamic-pituitary function have been described in patients with incidentally discovered adrenal adenomas and have been attributed to their subtle hypercortisolemic status.MethodsTo establish whether the central control of the...

Effect of long-term high-fat feeding on energy balance and liver oxidative activity in rats

The purpose of this work was to study the effect of early long-term high-fat feeding on energy balance and liver oxidative activity. To this end, rats aged about 30 d were fed a high-fat or a low-fat diet for 15, 30 or 60 d. Full energy balance and energy partitioning measurements were carried out. In addition, we measured hepatic mitochondrial and peroxisomal oxidative capacities. Serum levels of free triiodothyronine (T3) and leptin were also determined. Rats fed a high-fat diet showed an increase in metabolizable energy intake as well as in energy expenditure, while lipid gain over the whole period was lower than that expected due to a decrease in metabolic efficiency. An increase in serum free T3 levels was also found in rats fed a high-fat diet after 15 and 30 d. Statistically significant correlations between serum leptin levels and body fat mass were found after 15, 30 and 60 d of high-fat feeding. Finally, no variation in hepatic mitochondrial and peroxisomal fatty acid oxidation capacity was found in rats fed a high-fat diet for 15, 30 or 60 d. In conclusion, the results of the present study show that young Wistar rats fed a high-fat diet for up to 60 d are able to counteract, at least in part, obesity development.

Effects of triiodothyronine supplementation following modified Fontan procedure

AbstractPatients undergoing the modified Fontan procedure may develop low cardiac output postoperatively. Since thyroid hormone has important effects on cardiovascular function, the present study was undertaken to evaluate the influence of triiodothyronine supplementation. Ten consecutive patients under-going the Fontan procedure were administered intravenous triiodothyronine (0.4 mcg per kg) following surgery. Clinical outcome and thyroid hormone profiles were assessed and then compared to a previous series of patients undergoing the Fontan procedure who had not received triiodothyronine supplementation. Both groups initially demonstrated marked decreases in serum free triiodothyronine levels. The group which received triiodothyronine supplementation demonstrated a more rapid return of serum triiodothyronine levels to baseline [259±17 vs 121±15 pg/dl (p&lt;0.05) on the fifth postoperative day and 336±18 vs 178±12 pg/dl (p&lt;0.05) on the eighth day]. In addition, patients receiving supplemental triiodothyronine demonstrated more rapid recovery of total triiodothyronine, free thyroxine, total thyroxine and thyroglobulin levels. The group which received triiodothyronine supplementation had a shorter length of hospital stay [9±2 vs 14±3 (p&lt;0.05)] as compared to patients who did not receive exogenous triiodothyronine. The results of this study demonstrate that triiodothyronine supplementation aids in the recovery of thyroid hormone levels following Fontan procedure. This endocrinologic finding correlated with improved clinical outcome.

Thyroid function and serum thyroid binding proteins in prepubertal and pubertal children with chronic renal insufficiency receiving conservative treatment, undergoing hemodialysis, or receiving care after renal transplantation

OBJECTIVE: The abnormalities reported in some thyroid function tests in children with renal disease could be adaptive phenomena, shared by a variety of other nonthyroidal illnesses, or could reflect hypothyroidism. STUDY DESIGN: To answer this question, we studied thyroid function and serum thyroid binding proteins in 36 prepubertal and 23 pubertal patients with renal disease receiving three different therapies: conservative treatment, hemodialysis, and care after renal transplantation. RESULTS: During prepuberty, the serum concentration thyroxine binding globulin (mean ± SE) in the three groups of patients (294 ± 18, 303 ± 18, and 323 ± 16 nmol/L, respectively) was significantly lower than in prepubertal control subjects (451 ± 71 nmol/L). Only in prepubertal patients after renal transplantation (3583 ± 573 nmol/L) were serum thyroxine binding prealbumin values lower than in respective control subjects (5999 ± 908 nmol/L). The serum total thyroxine concentration in the three groups of patients (108 ± 41.9, 121 ± 5.7, and 123 ± 5.5 nmol/L, respectively) was significantly lower than in prepubertal control subjects (149 ± 10 nmol/L), whereas serum free thyroxine and serum albumin-bound thyroxine concentrations were similar to those in control subjects. The serum total triiodothyronine level in the three groups of patients (2.29 ± 0.82, 2.13 ± 0.13, and 2.01 ± 0.20 nmol/L, respectively) was significantly lower than in prepubertal control subjects (3.04 ± 0.24 nmol/L), whereas serum levels of free triiodothyronine and serum albumin-bound triiodothyronine were similar to those in prepubertal control subjects. During puberty, serum thyroxine binding globulin and serum thyroxine binding prealbumin levels in the three groups of patients were not statistically different from those in pubertal control subjects (309 ± 47 and 4950 ± 1230 nmol/L, respectively). Serum levels of total thy roxine, free thyroxine, albumin-bound thyroxine, total triiodothyronine, free triiodothyronine, and albumin-bound triiodothyronine were similar to those in pubertal control subjects except for pubertal patients undergoing hemodialysis. In all clinical groups the basal serum thyrotropin concentration was similar to those in respective control subjects. The frequency of goiter was increased in patients undergoing hemodialysis, probably as a result of iodide washout with dialysis. CONCLUSION: Children and adolescents with chronic renal insufficiency or end-stage renal disease or after renal transplantation do not have a primary abnormality of thyroid function and therefore are not candidates for thyroid hormone treatment. (J P EDIATR 1996;128:784-90)

Free triiodothyronine toxicosis in two adolescents

Two male adolescents had subtle symptoms and signs of thyrotoxicosis but normal levels of total and free thyroxine and total triiodothyronine. Serum concentrations of thyrotropin were undetectable in basal specimens and after administration of thyrotropin-releasing hormone; only free triiodothyronine values were elevated. An increase in serum levels of free triiodothyronine may be the earliest secretory abnormality of an overactive thyroid gland. (J P EDIATR 1994;124:276-8)

Reducing effect of nadolol on serum levels of free thyroid hormones in hyperthyroidism.

We evaluated the effect of the beta-adrenergic receptor blocking agent nadolol on serum levels of free thyroid hormones in 20 untreated patients with Graves' disease, aged between 17 and 57 years (mean +/- SD, 32.9 +/- 10.5). All the patients were treated with 30 mg of nadolol alone once-daily for 2 weeks, and clinical and laboratory parameters before and after the treatment were compared. Systolic blood pressure was depressed significantly (P < 0.001) from 132.7 +/- 11.1 mmHg to 122.8 +/- 10.9 mmHg. The resting pulse rate was also reduced significantly (from 110.3 +/- 9.2/min to 86.0 +/- 13.2/min, P < 0.001). Serum free thyroxine levels were reduced significantly from 7.1 +/- 3.1 ng/dl to 5.7 +/- 3.6 ng/dl (P < 0.05) and serum free triiodothyronine levels were reduced from 21.9 +/- 5.6 pg/ml to 17.2 +/- 6.9 pg/ml (P < 0.01). In the present study, the beta-adrenergic receptor blocking agent nadolol was newly found to have a reducing effect on serum free thyroxine, as well as free triiodothyronine concentrations.