Utilidad de los marcadores de remodelado óseo teniendo en cuenta el valor de referencia para el cambio / Clinical Utility of Bone Remodeling Markers Taking Into Account the Reference Value Change

La Modelación y el Remodelado de hueso son llevados a cabo a través del proceso de Recambio Óseo en sitios específicos llamados Unidades de Remodelación Ósea (URO). Este proceso puede evaluarse a través de marcadores bioquímicos de Formación y de Resorción que reflejan cambios globales del metabolismo esquelético. Estos marcadores de remodelado óseo son utilizados para investigación de enfermedades óseo-metabólicas, porque proveen información dinámica del metabolismo del hueso y pueden ser cuantificados en suero o en orina. La variación de estos marcadores se deben principalmente a variables preanalíticas, analíticas y biológicas y debe interpretarse teniendo en cuenta el Valor de Referencia para el Cambio significativo (VRC), que resulta de un cálculo en el que intervienen la variabilidad biológica (VB) del analito y el error aleatorio del método utilizado en el laboratorio.

The Modeling and Remodeling processes are conducted through the process of replacement bone at specific sites called Units Bone Remodeling (URO).These can be evaluated by biochemical markers of formation and resorption that reflect changes in skeletal metabolism. These markers of bone turnover are used for research óseo-metabolic diseases because they provide dynamic information of bone metabolism and can be quantified in serum or urine. The variation of these markers is mainly due to preanalytical, analytical and biological variables and should be interpreted taking into account the Reference Value Change (VRC), which results from a calculation in which the biological variability (VB) of the analyte and the random error of the method used in the laboratory are involved.

Rol del laboratorio en el diagnóstico del hiperaldosteronismo primario / Laboratory Role in the Diagnosis of Primary Aldosteronism

El aldosteronismo primario se considera actualmente el causante de un 8 a 12 % de los casos de hipertensión arterial. El aumento de su prevalencia es consecuencia de cambios en los criterios diagnósticos. El tamizaje inicial se realiza en el laboratorio determinando la relación aldosterona/actividad de renina plasmática, para lo que se requieren estrictas condiciones preanalíticas; condiciones de reposo o deambulación, evitando interferencias de drogas terapéuticas que pueden afectar el resultado, de obtención y de conservación de la muestra, entre otras. Debido a la alta variabilidad en la medición de la actividad de renina plasmática, (radioinmunoensayo operador dependiente), se está proponiendo el uso de la relación aldosterona/concentración de renina, (donde la concentración de renina se determina por un método automatizado) aunque aún no hay consenso. El método de tamizaje es fundamental para el inicio del estudio de un paciente e influye en la prevalencia actual. Una vez establecidos los valores de corte para cada laboratorio, los pacientes con tamizajes positivos deben ser sometidos a pruebas confirmatorias, por ejemplo sobrecarga con sodio, o supresión con fludrocortisona, para evidenciar la secreción autónoma de aldosterona. Una vez confirmada se debe diferenciar la causa; las principales son adenoma productor de aldosterona e hiperplasia adrenal bilateral. El diagnóstico temprano permite el tratamiento correcto, evitando comorbilidades causadas por la hipertensión arterial (HTA) y remodelaciones vasculares y cardíacas por el exceso de aldosterona. Los tratamientos clásicos para la HTA no siempre son de utilidad en el aldosteronismo primario, por ello es importante el diagnóstico de la patología.

Primary aldosteronism is nowadays considered the cause of 8 to 12 % cases of hypertension. The increase in its prevalence is due to changes in diagnostic criteria. Initial screening is performed in the laboratory by obtaining the aldosterone to plasma renin activity ratio, for which strict preanalytical conditions are required, including; supine or upright posture; interaction of therapeutic drugs which may alter results; sample extraction and conservation, among others. Given the high variability in the measurement of plasma renin activity and its complexity (RIA), the use of the aldosterone to renin concentration ratio is proposed (where renin concentration is determined by an automated immunoassay), although no consensus has been reached in this matter. The screening method is essential to primarily identify those patients who should be further studied, and it influences the statistics on actual prevalence of primary aldosteronism. Once cutoff values have been determined for each laboratory, patients with positive screening results must be further submitted for confirmation tests, such as salt-loading test or fludrocortisone suppression test, in which the autonomous secretion of aldosterone is confirmed. Then, the cause of the excessive aldosterone production must be determined. The most common are aldosterone producing adenoma and bilateral adrenal hyperplasia. Early diagnosis allows for the correct treatment, minimizing comorbidities caused by hypertension and by vascular and cardiac remodelation due to the excess of aldosterone. Classic treatment for hypertension is not always useful in patients with primary aldosteronism; this is why it is important to know how to diagnose the underlying pathology.

Cosecretion of glycosylated prolactin and non-glycosylated prolactin from childhood to the end of puberty.

BACKGROUND: Glycosylated prolactin (G-PRL) is considered as the major post-translational modification of prolactin (PRL) showing reduced lactotropic and mitogenic activities compared to non-glycosylated prolactin (NG-PRL). AIM: To evaluate the evolution of G-PRL in normoprolactinemic children and adolescents and to analyze possible variations in glycosylated/total prolactin (T-PRL) ratios. METHODS: T-PRL, G-PRL and NG-PRL were evaluated in 111 healthy female and male children and adolescents (4.1-18 years), classified as group 1 (Tanner I), group 2 (Tanner II-III) and group 3 (Tanner IV-V). G-PRL and NG-PRL were identified by chromatography on concanavalin-A-Sepharose. RESULTS: G-PRL/T-PRL (median-range): females, group 1: 0.59 (0.17-0.77), group 2: 0.56 (0.31-0.78), group 3: 0.60 (0.38-0.79); males, group 1: 0.64 (0.39-0.80), group 2: 0.61 (0.24-0.79), group 3: 0.62 (0.35-0.90); the p value is not significant among the different groups in both genders. G-PRL/T-PRL ratios do not change when comparing low (first quartile) versus high (third quartile) T-PRL levels in the different groups. CONCLUSION: Our study would appear to support cosecretion of G-PRL and NG-PRL from childhood to the end of puberty. Such cosecretion would not be dependent on sex steroid levels. It is important to point out that puberty does not change the proportions of G-PRL and NG-PRL.

Determinación del valor de corte de la relación aldosterona/actividad de renina plasmática para la detección de hiperaldosteronismo primario en hipertensión arterial esencial: estudio multicéntrico / Determination of the Aldosterone/Plasma Renin Activity Ratio for the Screening of Primary Hyperaldosteronism in Essential Hypertension: a Multicentric Study

El hiperaldosteronismo primario (HAP) es una afección caracterizada por la producción inapropiadamente elevada y una relativa autonomía del sistema renina-angiotensina. Estimaciones previas, basadas sólo en la evaluación de hipertensos con hipokalemia, consideraban al HAP como una causa poco frecuente de hipertensión (1%). Sin embargo, estudios actuales fundamentados en el cálculo de la relación aldosterona/ actividad de renina plasmática (RAA) arrojan una incidencia mayor (5-10%), siendo la hipertensión arterial (HTA) normokalémica la presentación más frecuente. Dada la amplitud de los valores de corte de la RAA, el Departamento de Suprarrenal de SAEM diseñó un estudio multicéntrico prospectivo en una población de Argentina con el objetivo de establecer nuestro propio valor y determinar así la prevalencia de HAP. Fueron estudiados 353 individuos de ambos sexos, 104 controles normotensos, sin antecedentes familiares de HTA y 249 pacientes hipertensos. Se indicó dieta normosódica y la suspensión de antihipertensivos que interfieran con el eje mineralocorticoideo. Las determinaciones de la actividad de renina plasmática (ARP), DIA-SorinRIA, y de aldosterona, RIA-DPC, fueron realizadas en un único laboratorio. Se realizó ionograma y se evaluaron parámetros clínicos y bioquímicos de síndrome metabólico. La RAA calculada según el percentilo 95 en los controles, fue establecida en la cifra de 36 como valor de corte para sospechar HAP en los hipertensos, requiriéndose una concentración de aldosterona >15 ng/ml. Con una RAA≥36, se realizaron pruebas confirmatorias de sobrecarga salina o de fludrocortisona. La RAA fue ≥36 en 31/249 pacientes, confirmándose HAP en 8 (7 adenomas y 1 hiperplasia), con una prevalencia del 3.2%. Los restantes no completaron estudios confirmatorios. La presencia de síndrome metabólico fue similar en los hipertensos con y sin HAP. En conclusión, este primer estudio multicéntrico argentino determinó nuestro valor de corte de la RAA en 36. Su aplicación permitió establecer una prevalencia de HAP del 3,2% que, aunque podría estar subestimada, resulta significativamente mayor que la previa histórica y concuerda con la incidencia referida en la bibliografía.

Primary hyperaldosteronism (PHA) or Conn's disease was classically suspected in the presence of hypertension (H) and hypokalemia. It was previously considered as a rare cause of H, being reported in only 1% of hypertensive patients. It can be caused by an adrenal adenoma (the former usual presentation) or by adrenal hyperplasia. But since the use of the aldosterone/plasma renin activity ratio (AAR) as the screening method in the last years, it is currently considered as almost the most frequent cause of secondary H., accounting for 5-10% of essential H. Plasma rennin activity (PRA) determination is a laborious procedure with low reproducibility and it directly affects the AAR; thus each laboratory must assess its own cut-off value. Therefore, in the Adrenal Department of the Argentine Society of Endocrinology and Metabolism (SAEM), we performed this multicentric prospective study of a population of Argentina with the aim of assessing our own AAR cut-off level in normotensive controls in order to apply it for PHA screening in essential hypertensive patients. We studied 353 adult subjects: 104 controls, aged 45,18 ± 13,78 years-old ( X±SD), with no history of arterial hypertension in their first-degree relatives and with two separate day-registry of blood pressure≤ 139/85 mmHg and 249 hypertensive patients, aged 51± 13,6 years-old ( X ± SD), with arterial blood pressure≥ 140/90 mmHg in the sitting position. Subjects with cardiac, renal, hepatic and neurological diseases were excluded as well as those with Cushing´s syndrome, hyperthyroidism, untreated hypothyroidism, diabetes mellitus and patients under glucocorticoids, oral contraceptive pills or estrogen therapy. A normal sodium diet was indicated and potassium was supplemented when needed. Blood was withdrawn between 8 and 10:00 a.m. with the subjects in the upright position. Aldosterone (A) was determined by DPC radioimmunoassay (RIA) and PRA, by DIA-Sorin RIA. The A normal levels are 4-30 ng/dl for ambulatory individuals on a normal sodium diet and the PRA normal values are < 3,3 ng/ml/h. In order to avoid false positive results in the hypertensive group, AAR was calculated when A was above 15 ng/dl. We measured the waist circumference and we determined the body mass index. Blood sodium, potassium, calcium, urea, creatinine, cholesterol, HDL-C, LDL-C, triglyceride and liver function tests were performed. Statistical Analysis and Results Since the AAR variable showed a non-normal distribution, the cut-off value was considered as the 95th percentile in the control group, which was calculated as 36. This is also in accordance to the function of the empirical distribution of Collings and Hamilton. In our 249 hypertensive patients, 31 had an AAR ≥ 36. PHA was confirmed in 8: seven has an adrenal adenoma and one had hyperplasia. The prevalence of PHA in our population was 3,2 %, with a 95th confidence interval ranging from 1,4 to 6,2 %. In the remaining 23 patients, confirmatory tests could not be completed. There was no correlation between the severity of the hypertension and the AAR value, with no statistical significant differences between those with or without PHA. Likewise, we found no correlation between PRA and advancing age. In hypertensive patients, metabolic syndrome was more prevalent than in controls, but it was present to the same extent in those with or without PHA. Conclusions To our knowledge, this is the first multicentric study performed in Argentina to determine the aldosterone/ plasma renin activity ratio in our normotensive control population. Our AAR value of 36 agrees with the levels reported in the international literature: thus an AAR ≥ 36 along with an aldosterone ≥ 15 ng/ml in hypertensive patients lead us to suspect PHA and to perform confirmatory tests. Applying these criteria, we found a prevalence of 3,2% of PHA in essential HTA. It is possible that this value may be underestimated due to the fact that confirmatory tests could not be completed in all the hypertensive subjects with an AAR≥ 36. In spite of this, our prevalence is significantly greater than the historical one and it lies in the range reported in the literature.

Hiperprolactinemia en la población infantojuvenil: un tema vigente / Hyperprolactinaemia in child an adolescent population: a current issue

La hiperprolactinemia constituye la altelaración endocrina más común del eje hipotálamo-hipofisario, aunque su prevalencia en la población infantojuvenil no está aún claramente definida. Además de la Prolactina (PRL) nativa (23Kda), se han descripto numerosas variantes moleculares, algunas de ellas con menor o ausente actividad biológica. Todo proceso que interrumpa la secreción de dopamina, interfiera con su liberación hacia los vasos portales hipofisarios o bloquee los receptores dopaminérgicos de las células lactotróficas, puede causar hiperprolactinemia. Si bien la patología tumoral constituye el diagnóstico de mayor relevancia, los prolactinomas son poco frecuentes en nios y adolescentes, aunque tienen en general una particular presentación clínica: de acuerdo con nuestra experiencia, el retraso puberal puede observarse en aproximadamente el 50% de las pacientes de sexo femenino. En pacientes con hiperprolactinemia asintomática debe evaluarse la presencia de proporciones alteradas de isoformas de PRL. La cromatografía en columna con sephadex G100, la precipitación con suspención de proteína A o con PEG y la ultracentrifugación constituyen los métodos más frecuentemente empleados para la detección de las distintas isoformas de PRL. En nuestra experiencia la B PRL constituyó el 6,6 - 32,6% de la PRL total y la BB PRL contituyó el 40 y el 72% de çesta en este gruo de pacientes. En cuanto al tratamiento por su efectividad y tolerancia, los agonistas dopaminérgicos constituyen la terapia inicial de elección en pacientes en edad pediátrica. La bromocriptina y la cabergolina han sido empleadas y con resultados similares a los de los pacientes adultos.

Controversies in the evolution of paediatric-adolescent varicocele: clinical, biochemical and histological studies.

OBJECTIVE: To study hormonal and histological parameters of paediatric-adolescent varicocele in order to know certain aspects of its natural history, in an attempt to find prognostic markers of testicular damage. DESIGN AND METHODS: In a prospective cross-sectional study, we evaluated 93 children and adolescents with left unilateral varicocele and 29 healthy males as control group. All of them were classified according to Tanner stage. Scrotal Doppler in both testes and GnRH and human chorionic gonadotrophin (hCG) tests were performed in all subjects. Surgery was performed in 28 patients and homolateral testicular biopsy in 18. RESULTS: Hormonal measurements of patients with varicocele were compared with a control group for each Tanner stage. Testicular biopsy specimens were analysed by light and electron microscopy. We only observed statistical differences in Tanner III patients in basal FSH (median and range) controls=1.70 (1.10-3.70) IU/l vs varicocele=4.20 (1.00-7.50) IU/l, P<0.05 and in Tanner IV patients in LH post-GnRH: controls=11.0 (7.50-15.0) IU/l vs varicocele=18.0 (5.10-29.0) IU/l, P<0.05 and in testosterone post-hCG: controls=9.50 (7.7-10.0) ng/ml vs varicocele=12.0 (6.2-23.0) ng/ml, P<0.01. No correlation was found between the various clinical grades of varicocele and hormonal measurements for each Tanner stage. No statistically significant differences were found between pre- and post-operative hormonal findings, either in basal levels or in maximal responses. On the other hand, no morphological abnormalities were observed by electron microscopy in germ cells, tubular wall and interstice. CONCLUSIONS: There appears to be no reliable biochemical marker in children and adolescents that may predict impaired testicular function. A significant size discrepancy between both testes, testicular pain and a hyperresponse to GnRH stimulation should continue to be, for the time being, the indications for surgery.

Macroprolactinemia in childhood and adolescence: a cause of asymptomatic hyperprolactinemia.

Asymptomatic hyperprolactinemias associated with altered proportions of molecular forms of circulating prolactin (PRL) have been reported in adults. The scarce references available in children and adolescents prompted us to report our experience in the evaluation and follow-up of patients with macroprolactinemia. We studied 5 patients (1 male and 4 females) aged 11.6-18 years with incidentally discovered asymptomatic hyperprolactinemia. Patients underwent repeated evaluations for a period of 3 months to 8 years, and their PRL levels remained elevated (34.4-516 ng/ml). Structural variants of PRL >/=45 kD ranged between 58.9 and 78.6%. Chromatographic profiles showed increases in Big Big PRL in the 5 cases, ranging between 40 and 72% (normal: 9-21%), and in Big PRL in 3 cases, ranging between 30.0 and 32.6% (normal: 5-25%). Little PRL was decreased in all cases, ranging between 20.6 and 41.1% (normal: 50-90%). In conclusion, upon detection of hyperprolactinemia with no clinical manifestations and no alteration of the remaining endocrine functions, macroprolactinemia should be considered as a possible diagnosis. The confirmed absence of functional alterations during the follow-up would favor a no-treatment approach and at the same time avoid repeating imaging studies.

Reproducibility and variability of the arginine test in normal adults. Comparison between sexes.

The biochemical diagnosis of growth hormone deficiency in adults (AGHD) remains controversial, mainly as regards stimulation tests and suggested cut-off lines. The insulin tolerance test proved to be the most effective growth hormone (GH) secretagogue in normal males, but a poor intra-individual reproducibility has been reported. Given the safety of the arginine test (AST), we decided to evaluate the incidence of false negatives (non responder normal subjects), its reproducibility and variability. Twenty five healthy non-obese volunteers (16 males, 9 females) with a chronological age range between 19 and 40 years, (mean: 29.8) were evaluated. AST was performed (0.5 g/kg i.v. infusion for 30 min), measuring GH (IRMA) at baseline (B), 30, 60 and 90 minutes, and it was repeated in the same subject 7 to 30 days later; in females both tests were performed in the early follicular phase. Results (median and range) were: 1st test B: 0.61 (0.35-22.60) micrograms/L; maximal response (Mx Resp) 10.00 (0.48-48.80) micrograms/L. 2nd test B: 0.50 (0.38-27.0) micrograms/L; Mx Resp 11.00 (0.50-47.70) micrograms/L. The statistical evaluation (Wilcoxon signed rank test) showed no differences between B vs. B and Mx Resp vs Mx Resp. Separated by sex, males showed: 1st test: B 0.45 (0.35-4.30) micrograms/L; Mx Resp 6.30 (0.48-48.80) micrograms/L. 2nd test B 0.46 (0.38-8.80) micrograms/L; Mx Resp 10.90 (0.50-47.70) micrograms/L, while females showed 1st test: B 5.20 (0.50-22.60) micrograms/L; mx Resp 14.00 (3.50-36.70) micrograms/L. 2nd test B 3.60 (0.75-27.00) micrograms/L; Mx Resp 13.00 (3.70-28.10) micrograms/L. The statistical comparison (Mann Whitney test) showed significant differences between both sexes in basal values of the first and second test (p < 0.001), and in the maximal response of the first test (p < 0.03). The statistical analysis did not show significant differences in delta increases between males and females, neither in the first AST nor in the second one. Considering GH values > or = 3 micrograms/L as a positive response, 4 males exhibited insufficient responses in both tests and other 2 males showed discordant results between tests 1 and 2. All females evaluated produced responses above 3 micrograms/L in both tests. The results of the present study demonstrate that, particularly in men, AST has no clear limit of normality while it shows good intra-individual reproducibility. In conclusion, at present the biochemical diagnosis of AGHD requires a clear and precise standardization which includes all variables that can modify the GH response to the stimulus used.

Reproducibility and variability of the arginine test in normal adults. Comparison between sexes.

The biochemical diagnosis of growth hormone deficiency in adults (AGHD) remains controversial, mainly as regards stimulation tests and suggested cut-off lines. The insulin tolerance test proved to be the most effective growth hormone (GH) secretagogue in normal males, but a poor intra-individual reproducibility has been reported. Given the safety of the arginine test (AST), we decided to evaluate the incidence of false negatives (non responder normal subjects), its reproducibility and variability. Twenty five healthy non-obese volunteers (16 males, 9 females) with a chronological age range between 19 and 40 years, (mean: 29.8) were evaluated. AST was performed (0.5 g/kg i.v. infusion for 30 min), measuring GH (IRMA) at baseline (B), 30, 60 and 90 minutes, and it was repeated in the same subject 7 to 30 days later; in females both tests were performed in the early follicular phase. Results (median and range) were: 1st test B: 0.61 (0.35-22.60) micrograms/L; maximal response (Mx Resp) 10.00 (0.48-48.80) micrograms/L. 2nd test B: 0.50 (0.38-27.0) micrograms/L; Mx Resp 11.00 (0.50-47.70) micrograms/L. The statistical evaluation (Wilcoxon signed rank test) showed no differences between B vs. B and Mx Resp vs Mx Resp. Separated by sex, males showed: 1st test: B 0.45 (0.35-4.30) micrograms/L; Mx Resp 6.30 (0.48-48.80) micrograms/L. 2nd test B 0.46 (0.38-8.80) micrograms/L; Mx Resp 10.90 (0.50-47.70) micrograms/L, while females showed 1st test: B 5.20 (0.50-22.60) micrograms/L; mx Resp 14.00 (3.50-36.70) micrograms/L. 2nd test B 3.60 (0.75-27.00) micrograms/L; Mx Resp 13.00 (3.70-28.10) micrograms/L. The statistical comparison (Mann Whitney test) showed significant differences between both sexes in basal values of the first and second test (p < 0.001), and in the maximal response of the first test (p < 0.03). The statistical analysis did not show significant differences in delta increases between males and females, neither in the first AST nor in the second one. Considering GH values > or = 3 micrograms/L as a positive response, 4 males exhibited insufficient responses in both tests and other 2 males showed discordant results between tests 1 and 2. All females evaluated produced responses above 3 micrograms/L in both tests. The results of the present study demonstrate that, particularly in men, AST has no clear limit of normality while it shows good intra-individual reproducibility. In conclusion, at present the biochemical diagnosis of AGHD requires a clear and precise standardization which includes all variables that can modify the GH response to the stimulus used.

Varicocele in prepubertal boys. Evaluation of clinical Doppler and hormonal findings.

Hormonal, clinical and scrotal Doppler findings were assessed in 16 prepubertal patients having unilateral varicocele. As already described in pubertal patients, Doppler studies made it possible to detect patterns of prolonged, intermittent or permanent reflux. An LH-RH test and an hCG test measuring LH, FSH and testosterone (T) were performed in all cases. Patients with varicocele showed (median and range): LH B (mlU/ml): 0.40 (0.40-2.1); LH Mx.: 3.7 (1.1-15); FSH B (mlU/ml): 1.95 (0.40-4.5); FSH Mx.: 4.9 (3.1-10); T B (ng/ml): 0.2 (0.1-1.5); T Post.: 2.25 (0.82-11.5). The control group showed: LH B (mlU/ml): 0.40 (0.4-0.85); LH Mx.: 2.15 (0.63-12) FSH B (mlU/ml): 1.45 (0.4-3); FSH Mx.: 4.25 (2.6-5.9); T B (ng/ml): 0.1 (0.1-0.3); T Post.: 3.26 (1.0-5.6). No significant differences were found between the hormonal results of the different groups classified according to the scrotal findings. Basal LH and FSH in grade 3 varicoceles were found to be significantly higher (p < 0.05) than those of the control group. Basal T, as well as the maximal response of both gonadotropins to LH-RH, and T response to hCG showed no significant differences with reference to the control group. Our findings provide indirect support to the notion that the gonadal damage would become detectable from puberty onwards.