Effects of Age and Health on the Euthyroid Reference Ranges for Serum Free Thyroxine and Free Triiodothyronine

1985 ◽  
Vol 24 (02) ◽  
pp. 57-65 ◽  
Author(s):  
J. E. M. Midgley ◽  
K. R. Gruner
Keyword(s):  
Lower Limit ◽  
Healthy Subjects ◽  
Thyroid Dysfunction ◽  
Reference Range ◽  
Free Thyroxine ◽  
Reference Ranges ◽  
Free Triiodothyronine ◽  
Serum Free ◽  
Young Subjects ◽  
Age Range

SummaryAge-related trends in serum free thyroxine (FT4) and free triiodothyronine (FT3) concentrations were measured in 7248 euthyroid subjects (age-range 3 months to 106 years). 5700 were patients referred to hospitals for investigation of suspected thyroid dysfunction, but who were diagnosed euthyroid. 1548 were healthy blood donors (age-range 18-63 years) with no indication of thyroid dysfunction. FT4 concentrations were little affected by the age, the sex or the state of health of the subjects in either group. Serum FT3 concentrations were significantly affected by both age and health factors. The upper limit of the euthyroid reference range for young subjects up to 15 years was about 20% higher (10.4 pmol/1) than for adult subjects older than 25 years (8.8 pmol/1). The change in the upper limits typical of young subjects to that typical of adults occurred steadily over the decade 15–25 years. After this age, little further change occurred, especially in healthy subjects. Additionally, the lower limit of the euthyroid range for FT3 was extended by the inclusion in the reference group of patients referred to hospitals. Compared with the lower limit of the FT3 range for healthy subjects (5 pmol/1), the corresponding limit for referred subjects (young or adult) was 3.5–3.8 pmol/1. Broadening of the FT3 reference range was probably brought about by a significant number of patients in the hospital-referred group with the “1OW-T3 syndrome” of mild non-thyroidal illness. Accordingly, FT3 was inferior to FT4 in the discrimination of hypothyroidism, as FT4 was unaffected by this phenomenon. Effects of age and non-thyroidal illness on serum FT3 concentrations require great care when selecting subjects for a laboratory euthyroid reference range typical of the routine workload. Constraints on the choice of subjects for FT4 reference ranges are less stringent.

scholarly journals Falsely High Serum Free Triiodothyronine and Free Thyroxine Concentrations Attributable to Anti-Diiodothyronine and Anti-Triiodothyronine Antibodies

2005 ◽  
Vol 51 (6) ◽  
pp. 1071-1072 ◽  
Author(s):  
Kunihiro Iwahara ◽  
Chizuko Tanabe ◽  
Kozo Nishiyama ◽  
Hiroyuki Ohashi ◽  
Masato Maekawa
Keyword(s):  
High Serum ◽  
Free Thyroxine ◽  
Free Triiodothyronine ◽  
Serum Free

scholarly journals Misleading results from immunoassays of serum free thyroxine in the presence of rheumatoid factor

1997 ◽  
Vol 43 (6) ◽  
pp. 957-962 ◽  
Author(s):  
Anthony G W Norden ◽  
Rodwin A Jackson ◽  
Lorraine E Norden ◽  
A Jane Griffin ◽  
Margaret A Barnes ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Rheumatoid Factor ◽  
Equilibrium Dialysis ◽  
Thyroid Stimulating Hormone ◽  
Normal Serum ◽  
Free Thyroxine ◽  
Free Triiodothyronine ◽  
Serum Free ◽  
Serum Free Thyroxine ◽  
Stimulating Hormone

Abstract A novel interference with measurements of serum free thyroxine (FT4) caused by rheumatoid factor (RhF) is described. We found misleading, sometimes gross, increases of FT4 results in 5 clinically euthyroid elderly female patients with high RhF concentrations. All 5 patients had high FT4 on Abbott AxSYM® or IMx® analyzers. “NETRIA” immunoassays gave misleading results in 4 of the 5 patients; Amerlex-MAB® in 2 of 4 patients; AutoDELFIA®in 2 of the 5; and Corning ACS-180® and Bayer Diagnostics Immuno 1® in 1 of the 5. BM-ES700® system results for FT4 in these women remained within the reference range. Results for serum T4, thyroid-stimulating hormone, free triiodothyronine, thyroid-hormone-binding globulin, and FT4 measured by equilibrium dialysis were normal in all 5 patients. Drugs, albumin-binding variants, and anti-thyroid-hormone antibodies were excluded as interferences. Addition to normal serum of the RhF isolated from each of the 5 patients increased the apparent FT4 (Abbott AxSYM). Screening of 83 unselected patients demonstrated a highly significant positive correlation between FT4 (Abbott AxSYM) and RhF concentrations. Discrepant, apparently increased FT4 with a normal result for thyroid-stimulating hormone should lead to measurement of the patient’s RhF concentration.

Variations in Serum Free Thyroxine Concentration Within the Reference Range Predicts the Incidence of Metabolic Syndrome in Non-Obese Adults: A Cohort Study

Thyroid ◽  
2017 ◽  
Vol 27 (7) ◽  
pp. 886-893 ◽  
Author(s):  
Ladan Mehran ◽  
Atieh Amouzegar ◽  
Mahmood Bakhtiyari ◽  
Mohammad Ali Mansournia ◽  
Parnian Kheirkhah Rahimabad ◽  
...  
Keyword(s):  
Metabolic Syndrome ◽  
Cohort Study ◽  
Reference Range ◽  
Free Thyroxine ◽  
Obese Adults ◽  
Serum Free ◽  
Serum Free Thyroxine

Circadian thyrotropin variations are preserved in normal pregnant women

1995 ◽  
Vol 133 (1) ◽  
pp. 71-74 ◽  
Author(s):  
Elio Roti ◽  
Luigi Bartalena ◽  
Roberta Minelli ◽  
Mario Salvi ◽  
Eliana Gardini ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Pregnant Women ◽  
Free Thyroxine ◽  
Third Trimester ◽  
Circadian Variations ◽  
Free Triiodothyronine ◽  
Serum Free ◽  
Trimester Pregnancy ◽  
Serum Tsh ◽  
Serum Free Thyroxine

Roti E, Bartalena L, Minelli R, Salvi M, Gardini E, Pistolesi A, Martino E, Braverman LE. Circadian thyrotropin variations are preserved in normal pregnant women. Eur J Endocrinol 1995;133:71–4. ISSN 0804–4643 Serum thyrotropin (TSH) concentration circadian rhythm is abolished in many endocrine and nonendocrine diseases. In the present study we have measured serum TSH concentration over 24 h every 2 h in second and third trimester pregnant women. During the 24-h period, serum free thyroxine and free triiodothyronine concentrations did not change significantly. In contrast, serum TSH concentrations demonstrated significant circadian variations both in the second and third trimester pregnant women (p<0.02 and p <0.005, respectively). In summary, second and third trimester pregnancy is associated with a normal circadian TSH rhythm. Elio Roti, Centro per lo Studio, Prevenzione, Diagnosi e Cura delle Tireopatie, University of Parma, via Gramsci 14, 1-43100 Parma, Italy

scholarly journals Serum Adenosine Deaminase Values in Healthy People

2020 ◽  
Keyword(s):  
Adenosine Deaminase ◽  
Healthy Subjects ◽  
Reference Range ◽  
Mean Value ◽  
Normal Serum ◽  
Healthy People ◽  
Reference Ranges ◽  
Percentile Method ◽  
The Mean ◽  
Almost All

The purpose of this study is to determine the activity of serum adenosine deaminase (ADA) in healthy people, in connection with significant differences in published reference ranges from different authors. In our study, we examined 160 healthy subjects aged 18 to 84, of whom 64 were men and 96 women. We have determined serum adenosine deaminase levels using a method based on the ability of the enzyme adenosine deaminase to catalyze the deamination of adenosine to inosine and ammonia. The catalytic concentration is determined spectrophotometrically by the rate of reduction of NADH measured at 340 nm. We found that normal serum ADA values among our healthy subjects are higher than the recommended reference range for the method we use, namely below 18 U/l. Using the percentile method, we worked out the following reference ranges: for women 14.53 - 25.73 U/l and for men 18.46 – 27.50 U/l. For women, the mean value is 21.07 U/l, and for men 21.30 U/l. At 95% CI, the serum ADA values of almost all subjects included in the study are within the recommended and other authors range of 11.50 - 25.00 U/l.

scholarly journals SAT-047 Adoption of an Age Adjusted Testosterone Reference Range Reduces Referrals to Endocrine Clinic and New Prescriptions of Testosterone

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Charlotte Dewdney ◽  
Heidi Mendoza ◽  
Rosemary Clark ◽  
Sandra MacRury ◽  
Rod Harvey ◽  
...  
Keyword(s):  
Lower Limit ◽  
Reference Range ◽  
Age Groups ◽  
Male Hypogonadism ◽  
Reference Ranges ◽  
Endocrine Society ◽  
Testosterone Levels ◽  
Referral Criteria ◽  
Before And After ◽  
The Impact

Abstract Testosterone levels decline with age. However, until recently well defined harmonised age and/or obesity (BMI &lt;30kg/m2) adjusted reference ranges did not exist.1 There is also a lack of international consensus on whether an age adjusted reference range (RR) should be used to define the syndrome of hypogonadism in men. Our local referral guideline suggests referral to endocrinology is appropriate if morning testosterone is &lt;9.4nmol/L similar to the Endocrine Society Clinical Practice Guideline.2 In mid 2018 our laboratory adopted the published all men age adjusted RR1. We sought to; i) investigate clinic referrals before and after adoption of the all men age adjusted RR and, ii) to model the impact on referrals and prescription of testosterone replacement therapy (TRT) had we adopted either the lower limit of either all men or non-obese age adjusted RR as our referral criteria. Despite similar numbers of testosterone levels being measured in the laboratory, referrals to endocrine clinic for investigation of male hypogonadism fell by 52% (n=101 vs 48) in the one year following the introduction of the new age adjusted RR, with a corresponding reduction in prescriptions for testosterone. Mean testosterone concentration (6.7±2.5 vs 6.4±3.9nmol/L [mean±SD], NS), and age (51±13.9 vs 50±17.9 years, NS) of individuals referred were similar before and after the change of RR. Of the 101 patients referred for investigation of hypogonadism prior to the new RR mean testosterone concentrations were 8.5±4.5, 7.3±4.1, 6.8±3.6, 6.7±2.1 & 6.6±1.6nmol/L, with 39, 71, 39, 40 & 17% of the 87 patients seen in clinic being prescribed TRT in age groups 19-39 (n=28), 40-49 (n=7), 50-59 (n=33), 60-69 (n=20) &70-79 (n=6) respectively, excluding those with a history of anabolic steroid use or Klinefelter’s syndrome. Mean BMI was 30.9±4.4kg/m2, which was similar between age groups. Had the lower limit of normal of the all men testosterone RR been employed as our referral criteria in the preceding year, 23.8% (24/101) of referrals would not have met referral criteria, and 26.2% (n=11/42) of those receiving a prescription would potentially not have received a trial of TRT. In contrast, had the non-obese age adjusted RR had been adopted for all men 13.9% (14/101) of referrals would not have met referral criteria and, of those prescribed testosterone, 2.4% (n= 1/42) would not have received a trial of TRT. In conclusion, adoption of the all men age adjusted RR for testosterone has been associated with a significant fall in referrals for investigation of male hypogonadism. However, modelling of historical clinic data would suggest that some non-obese individuals miss out on a therapeutic trial of TRT, especially if the all men, rather than non-obese, age adjusted RR is adopted. Reference: (1) Travison et al, J Clin Endocrinol Metab, 2017,102(4):1161-1173, (2) Bhasin S et al,. J Clin Endocrinol Metab. March 2018;103(5):1715-1744.

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