Search

An 18-year-old woman was referred by her GP to the endocrinology department of the University Hospital of Bordeaux on suspicion of premature ovarian failure because of a disorder of the menstrual cycle and pathological results of biological exploration of the gonadotropic axis. Repeatedly-found elevated concentrations of FSH contrasted with a normal concentration of LH leading to a hypothesis of ovarian failure. However, different investigations favoured an analytical interference. The presence of heterophilic antibodies or anti-mouse antibodies (HAMA) was unlikely but, finally, a complex combining FSH and autoantibody (called macro-FSH) was evidenced.

Identifying analytical interference is a challenge for the medical biologist in providing advice to the prescriber. Indeed, these analytical interferences often have deleterious consequences on the care of patients. Understanding their mechanisms and mastering corrective procedures is essential to limit these management errors. Faced with the many questions from clinicians in current practice, we propose an algorithm for managing a sample when interference is suspected.

Steroid hormone measurement, first developed with radioimmunoassay, is now becoming easier with the use of automated platforms of immunoassay. However, some hormones remain uneasily detectable because of their low blood concentration, their structural homology or the presence of interferences. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) can be considered as an alternative to immunoassays. This approach allows the simultaneous determination of several parameters thanks to its selectivity led by the detector mass spectrometer and the separate dimension of chromatography liquid. In addition, recourse to UHPLC (ultra high performance liquid chromatography) allows improving selectivity and sensitivity while limiting the samples volumes. The "ready-to-use" kits are now available and added to the "homemade" techniques developed by laboratories, thus giving opportunity for measurement of a wide steroid panel with only one sample. Finally, mass spectrometry methods, including a prior extraction step, allow the use of varied biological fluids (blood, urine, saliva…). Also, several clinical indications could gain from mass spectrometry, especially when hormone levels are low, when several steroids have to be identified, when the sample volume is low. However, this technology represents an important financial investment and in-depth staff training. In addition, some steroids are not easily quantifiable by mass spectrometry. It is likely by immunoassay and mass spectrometry, well-matched technologies, that we could answer the best to clinical questions about steroids.

Erythropoietin (EPO) is the principal haematopoietic growth factor of the red blood cell line. Its major role is to stimulate the red blood cell production. EPO synthesis by peritubular cells in the kidney is regulated by oxygen concentration and must lead adaptation of the organism to face many different physiological situations. An imbalance can lead either to anaemia or polycythemia. Synthetic EPO, so-called recombinant, has definitively changed the treatment in the anaemia of chronic renal failure and regularly find new indications, legal (anaemia of cancer, anaemia of chronic inflammatory syndromes, myelodysplastic syndromes, neurology, cardiology...) or illegal (doping substance in sport). This article reviews the physiology, the role and the indications of EPO in clinical routine practice and define why and how EPO should be measured. We also focus on the analytical requirements for serum EPO concentration determination, especially in the differential diagnosis of polycythemias (secondary polycythemia/Polycythemia Vera).

Estradiol (E(2)) - similarly to testosterone - is a hormone mainly bound to SHBG and albumin in serum. Only the non SHBG-bound (free and albumin-bound hormone, i.e. bioavailable) hormone diffuses easily from circulation to tissues and is available for target cells. Bioavailable hormone measured or calculated seems to represent the best access to bioactive hormone concentration. Several studies reported that this bioavailable E(2) could be usefully measured for the understanding of chronic diseases in men or women, such as osteoporosis, cardiovascular disease and Alzheimer's disease. E(2) assays require a high sensitivity to assess low concentrations. It is currently difficult to know if bioavailable E(2) is really implicated or not in a given pathology but its interest is reported in many epidemiological studies.

Serum cortisol free fraction is responsible for its physiological function. Determination of serum total cortisol concentration does not allow accurate evaluation of hypothalamic pituitary adrenal axis when there is a quantitative variation in serum transcortin. Although free cortisol can be assayed by salivary or urinary cortisol measurements, these methods can not be easily applied in intensive care units. Free plasmatic cortisol measurement could provide a better reflect of circulating cortisol in patients with critical illness whom have a decreased concentration of binding proteins and whom adrenal status is an important prognostic factor. Free cortisol can be measured after separation from bound cortisol, calculated with equation based on equilibrium binding or evaluated by cortisol/CBG ratio. In various studies, free plasmatic cortisol allows in critical care patients a better appreciation of adrenal status than total cortisol and be more differential than total cortisol increment after stimulation with synacthen used to diagnose "relative adrenal insufficiency".

A boy presented at birth dyspnea, jaundice, meteorism and hypospadias; biochemical testing revealed hyponatremia. He benefited on day 4 of neonatal screening for hypothyroidism and congenital adrenal hyperplasia (CAH) and assays showed high concentrations of 17-OHP and TSH. Because of clinical features and hyponatremia, the diagnosis of CAH was plausible. A serum control (17-OHP and TSH) carried out on day 8 showed a normal concentration of 17-OHP and a persistently elevated concentration of TSH confirmed by a second assay a few days later. A 131I scan of neck revealed an ectopic lingual thyroid. The considerable progression of false positive screening tests for CAH is mainly due to the increasing number of premature babies. We show by a retrospective analysis (7 yrs), that children with hypothyroidism also present frequently higher concentrations of 17-OHP than normal children. However, whatever the aetiology (apart from CAH), the concentrations of 17-OHP rapidly normalise.

Diagnosing primary aldosteronism, a hypertensive endocrine disease, is difficult because of an ill-defined frequency, various clinical forms and multiple diagnostic criteria. Current recommendations rest upon aldosterone and renin or renin activity determinations, the main point being to investigate aldosterone secretion with regards to of its main stimulus, renin. Proponents of the renin assay argue that it is easy and reliable. Proponents of the renin activity assay favour this method because of multiple epidemiological studies. Whatever the method used, each laboratory has to establish its critical thresholds in relation to the kits used. Extensive comparative studies would be useful to appreciate their relative benefits.

The tetra-peptide Acetyl-Ser-Asp-Lys-Pro (Ac-SDKP) generated by the cleavage of thymosine beta4 inhibits the proliferation of hematopoietic stem cells and the proliferation and secretion of fibroblasts in the myocardium and the glomeruli. The clinical administration of Ac-SDKP has been proposed and partially investigated. The peptide could protect hematopoietic stem cells during anti-neoplastic treatments leaving cancerous cells unprotected. As it opposes the effects of TGFbeta it could prevent fibrosis after myocardial infarcts and glomeruli fibrosis during the natural course of diabetic nephropathy. However, until now the expected benefits of such a treatment are based on an indirect consideration. Indeed, the degradation of Ac-SDKP is due to the action of the angiotensin-converting enzyme. Interestingly, the blocking of this enzyme both improves the above-mentioned fibrosis and increases the plasma levels of Ac-SDKP. Should the therapeutic effects prove solid, and therapeutic levels be established assaying Ac-SDKP could be an interesting marker of therapeutic efficiency.

The follow-up of differentiated carcinomas is based on the detection of thyroglobulin (Tg) in the serum. Tg assays are immunoassays that may be hampered by autoantibodies directed against Tg. To avoid this problem some authors advocated the use of mRNA extraction and RT-PCR amplification. Quantitative methods have been developed to achieve a good analytical sensitivity. These techniques may then be alternative to the Tg assay when anti-Tg antibodies are present in the serum should it be proven they display pronostic values reliable enough for clinical diagnosis use.

Objectives: Patients treated by (131)I may require blood sampling in the days following its administration. We investigated the safety of such samples in terms of radioactivity and the possible disturbance of the analyses by these "131I-spiked" samples., Method: 1) The radioactivity of blood samples from 131I-treated patients was measured (dose rate, surface activity, total activity) ; 2) The risk for the personnel was subsequently evaluated and ; 3) The interference of this 131I-generated radioactivity on the results of routine automated and IRMA assays was investigated., Results: 1) All RA measures but two were found below the European limits ; 2) Irradiation of personnel was negligible ; 3) The faint radioactivity did not disturb any analyses., Conclusion: These data demonstrate the safety that results from the negligible radioactivity in these blood samples.

The evolution of techniques has increased the number of diagnosed thyroid papillary microcarcinoma challenging the previous therapeutic guidelines. We have studied all thyroid cancers in our data base (from 1953 to 1994, N = 698). One-hundred and eleven were papillary microcarcinomas (none before 1967): 83 M0N0, 24 M0N+ et 4 M+. One-hundred and eight pathologic slides could be obtained and were checked by one of us (pathologist). The mean follow-up was 8.6 yr [1-28]. Two clinical and pathological features were different between M0N0 and M0N+ (groups: i) the sex-ratio, 12 vs 50% men (M0N0 vs M0N+, p < or = 0.0001), ii) the invasiveness of the tumor, 54/83 vs 20/24 (M0N0 vs M0N+, p = 0.01). All patients received a suppressing treatment by thyroid hormones (except lobectomy). The other treatments were: for 64/83 M0N0 a total thyroidectomy followed by a I131 treatment, for the remaining no I131 (15 partial thyroidectomies and 4 total thyroidectomies). None of the M0N0 patients displayed metastasis or cancer relapse. All patients M0N+ had a total thyroidectomy followed by a I131 treatment. Among the latter, I had a major node evolution, the death was attributed to the cancer at the age of 83 after a 6 yr long evolution. Among the 4 patients considered as metastatic. 1 was poorly differentiated. For the remaining 3, the thyroidal origin of the metastasis was not clear. In summary, the papillary microcarcinomas display a good prognosis if devoid of metastasis. We propose the following guidelines: a total thyroidectomy followed by a I131 treatment and suppressing treatment if clinical nodes, or non-encapsulated tumor or multifocal tumor. For solitary tumors, well encapsulated a lobectomy appears sufficient.

High concentrations of lipoprotein (a) (Lp(a)) are associated with an increased risk of atherosclerotic vascular disease. Lp(a) synthesis is mainly under genetic control but many endocrine disturbances may modulate Lp(a) plasmatic concentrations. There is no agreement upon Lp(a) variations in patients under a hypocaloric diet. This study was undertaken to assess this point in obese females subjected to a 1100 kcal/d diet. Ninety-two obese patients (42.4 +/- 10.4 yr old, BMI 33.9 +/- 5.6 kg/m2) came once a week as out patients during 9 weeks. Lp(a) concentrations distribution was highly skewed. The threshold Lp(a) concentration for a significant cardiovascular risk is estimated at 0.3 g/l. Concentrations above 0.3 g/l were found in 29/92 patients (31%). If the patients were distributed in 2 groups according to their Lp(a) values (< or = ou > 0.3 g/l), the BMI, total cholesterol or triglycerides were not different. There were no significant correlation between Lp(a) and age, total cholesterol or triglycerides. After 9 weeks BMI and total cholesterol values decreased (-1.6 +/- 3.4 kg/m2 and -0.17 +/- 0.68 mmol/l, respectively). Lp(a) concentrations were unchanged (0.3 +/- 0.3 vs 0.3 +/- 0.3 g/l). There were no significant correlation between Lp(a) variations and age, BMI or initial Lp(a) concentrations. No significant decrease of Lp(a) could be detected even in the sub-group of patients with initial concentrations of Lp(a) > 0.3 g/l or even in a sub-group with Lp(a) > 0.7 g/l (n = 7). Under our conditions, weight loss is not associated with a decrease of Lp(a) concentrations suggesting that in a given obese a single determination is enough to assess his Lp(a)-related atherosclerotic risk.