Endocrine Abstracts

Quantitation of insulin in human plasma was first achieved by Berson and Yallow in 1960, as reported in their seminal paper describing radio-immunoassay (J Clin Invest. 1960(7)39:1157). Despite the wider availability of insulin assays, improvements in immunoassay design and the advent of mass-spectrometric methods to quantitate insulin, insulin assays are used far less than other hormone assays in endocrinological investigations. This is largely due to the dynamic nature of in...

Heterophilic antibody interference in serum TSH immunoassays can result in misdiagnosis of patients with suspected thyroid disease. Rheumatoid factor (RhF) is an immunoglobulin with reactivity to the Fc portion of human IgG. Some RhF species also cross-react with animal immunoglobulins so have the potential to act as heterophile antibodies. As part of the Cambridge Supra-Regional Assay service for thyroid function testing five serum samples with strongly positive RhF and posit...

A 56-year-old woman presented with progressive swelling of her face and fatigability. Investigating for Cushing’s, her 24-hour Urine Free Cortisol was negative at 43 and 70nmol/24hr (Reference interval or R.I. < 146 nmol/24hr) with overnight dexamethasone suppression test showing full suppression of cortisol to 34nmol/l. Her short synacthen test was normal at 30-minute cortisol of 753nmol/l (R.I.>420); on Zumenon. Other pituitary function tests were unremarkable b...

Testosterone in serum may be unbound (free), or bound to either sex hormone binding globulin (SHBG) or albumin. Consequently, ‘total’ serum testosterone analysis may be misleading in situations where binding protein concentrations are abnormal. Current methods for estimating the biologically active (bio-available) serum testosterone concentration involve physical separation of testosterone fractions and are not amenable to high-throughput analysis. The use of automat...

Background: Elevated TSH concentration should be assessed and treated with caution because of the possibility of transient thyroid dysfunction, or, in rare cases, measurement interference. We describe a case with a rare cause of elevated TSH level in a 39-year-old mother and her four children.Case Summary: A 39-year-old lady was referred with a long history of high serum TSH ranging between 18.9 to 38.7 (reference interval 0.4-4.0 mU/l) with FT4 concentr...

Introduction: Hydrocortisone is the main treatment for congenital adrenal hyperplasia (CAH) in children. The optimal biochemical monitoring and replacement regimen of these children continues to be debated. We explored variations in blood spot 17α-hydroxyprogesterone (17-OHP) levels.Methods: Single centre retrospective cross-sectional study of children with 21-hydroxylase deficiency aged <18 years. Patients treated with hydrocortisone who had dr...

Positive interference in free thyroxine (fT4) and free triiodothyronine (fT3) immunoassays is well known, however we report a rare case of negative interference in the Roche fT4 and fT3 immunoassays in a 3-year-old girl with undetectable fT4 and fT3. She presented with increasing tiredness, abdominal pain, pain in her lower limbs and constipation. Examination was unremarkable. Thyroid func...

Introduction: The benefits of growth hormone (rGH) replacement during the transition from childhood to adulthood are well established. In adulthood rGH dose is optimized by titrating to serum IGF-I concentration. The use of non-specific IGF-I reference ranges may result in erroneous assessment of IGF-I concentration and inappropriate rGH dosing.Methods: IGF-I methods and reference ranges across 9 UK centres were reviewed. Immulite IGF-1 results for a 12 ...

Liquid chromatography tandem mass spectrometry (LC–MS/MS) methods are considered superior to immunoassay for the analysis of serum 25-hydroxy vitamin D (25-OHD) due to improved performance and potential cost benefits. As LC–MS/MS is appropriate for the analysis of other clinically relevant hormones tandem mass spectrometers are becoming commonplace in UK clinical laboratories. However, like immunoassay, LC–MS/MS methods are not foolproof and inappropriate use of...

Clinical guidance recommends titrating the dose of metyrapone against serum cortisol concentrations. These serum samples are usually measured by immunoassays; however it has been well documented that there are interferences in these assays in patients with altered steroid metabolism due to a pathological process or drug treatment. The increasing availability of mass spectrometry (MS) assays for steroid hormones may circumvent this issue and assays that measure multiple steroid...