[Unexpected high values of TSH: the presence of high molecular weight forms (macro TSH) must be investigated]. / Valores inesperadamente elevados de TSH: a presença de formas de alto peso molecular ("macro TSH") deve ser investigada.

The laboratory methods usually employed for the measurement of serum TSH present sensitivity and specificity levels, both analytical and clinical, are highly satisfactory. Additionally, the methodologies are quite robust, so that false-positive and false-negative results are rare and unexpected. In this paper we describe two individuals quoted as euthyroid clinically, with no reference to autoimmune diseases, and no reference to the use of exogenous TSH, that presented with normal to extremely high serum TSH levels, depending on the method employed for analysis. In the three tested methods, serial dilution showed that the real TSH levels were between 250 and 300 mUI/L. In both cases the increment in TSH levels were due to the presence of TSH-binding proteins, forming high molecular weight complexes ("macro TSH"), well characterized by gel filtration chromatography on Superdex S-200 column. In one of the patients the binding protein was characterized as being IgG by protein-G binding study. In the other case, protein-G binding as well as anti-IgM binding failed to characterize the protein. These two cases call attention to the importance of the clinical-laboratory correlation and suggest the need that the presence of "macro TSH" must be investigated in patients with unexpectedly high TSH values.

Estimation of diabetes risk in Brazilian population by typing for polymorphisms in HLA-DR-DQ, INS and CTLA-4 genes.

The study aimed to further characterise HLA encoded risk factors of type 1 diabetes (T1D) in Brazilian population and test the capability of a low resolution full-house DR-DQ typing method to find subjects at diabetes risk. Insulin and CTLA-4 gene polymorphisms were also analysed. The method is based on an initial DQB1 typing supplemented by DQA1 and DR4 subtyping when informative. Increased frequencies of both (DR3)-DQA1*05-DQB1*02 and DRB1*04-DQA1*03-DQB1*0302 haplotypes were detected among patients. DRB1*0401, *0402, *0404 and *0405 alleles were all common in DQB1*0302 haplotypes and associated with T1D. (DRB1*11/12/1303)-DQA1*05-DQB1*0301, (DRB1*01/10)-DQB1*0501, (DRB1*15)-DQB1*0602 and (DRB1*1301)-*0603 haplotypes were significantly decreased among patients. Genotypes with two risk haplotypes or a combination of a susceptibility associated and a neutral haplotype were found in 78 of 126 (61.9%) T1D patients compared to 8 of 75 (10.7%) control subjects (P < 0.0001). Insulin gene -2221 C/T polymorphism was also associated with diabetes risk: CC genotype was found among 83.1% of patients compared to 69.3% of healthy controls (P=0.0369, OR 1.98) but CTLA-4 gene +49 A/G polymorphism did not significantly differ between patients and controls. Despite the diversity of the Brazilian population the screening sensitivity and specificity of the used method for T1D risk was similar to that obtained in Europe.

[Parathyroid carcinoma]. / Carcinoma de paratiróide.

Parathyroid carcinoma is a rare condition, comprising less than 1% of the cases of primary hyperparathyroidism (PHP). Nonetheless, due to its aggressiveness, and having prognosis dependent on the precocity of diagnosis and radical therapeutic approach, it is paramount that the clinical suspicion be made before surgery. Clinical presentation is typical of severe PHP, with a parathyroid tumor >1.5 cm, usually palpable. The pathologic features sometimes are difficult to characterize. Our experience with this condition (from 1983 to 2004) includes 7 cases, all symptomatic, hypercalcemic syndrome and bone disease present in most of them. In 6/7 the tumor was palpable, and in all the biochemical profile was compatible with severe PHP. Three patients died of complications of hypercalcemia. Recent findings point to a mutation on the gene HRPT2 as the molecular base for the development of this kind of tumor. The therapeutic approach is surgical and should include ipsilateral thyroidectomy and cervical exploration in order to find possible local metastasis. Post-surgical complications (mainly hypocalcemia) are proportional to the pre-existing metabolic alterations. The long-term prognosis depends upon the precocity of diagnosis, surgical success and control of hypercalcemia. New therapeutic approaches, based on bisphosphonates and calcimimetic drugs, as well as the possibility of genetic diagnosis, tend to ameliorate the prognosis of this severe affection.

[Tolerance of the oral clonidine test in 180 patients: efficacy of the volemic expantion in controlling arterial hypotension]. / Tolerância ao teste da clonidina em 180 pacientes: estudo da eficácia da expansão volêmica para o controle de hipotensão arterial.

Clonidine stimulation test is widely used to evaluate growth hormone secretion. Side effects are somnolence (35%) and arterial hypotension (AH) (5%). The aims of this paper were to evaluate the tolerance to this test regarding blood pressure (BP) decrease, sedation and the efficacy of saline resuscitation to prevent AH. BP was measured at basal, 60 and 120 min. Sedation was determined by the Ramsay scale. Patients were divided into two groups: Group 1 (n = 80) received saline resuscitation only upon severe AH (drop of mean BP [MBP] > 20% from initial MBP) and/or postural hypotension; Group 2 (n = 100) received saline resuscitation from the beginning of the test. Both groups presented a significant MBP fall and 75% presented somnolence at 60 min. MBP drop did not correlate with either sedation or the clonidine dose. Group 1 presented more hypotension (59% x 28%) and greater MBP drop at 60 min. Only one patient had an asthma attack. We conclude that the hypotension effects caused by oral clonidine diminish with saline resuscitation since the beginning of the test. This test must have specialized medical support with strict BP evaluation and precocious intervention when needed.

[Continuous glucose monitoring: a critical appraisal after one year experience]. / Monitorização contínua de glicose: análise crítica baseada em experiência ao longo de um ano.

Conventional assessment of glycemic control in diabetes mellitus (DM) includes blood glucose attention to glycemia and glycated hemoglobin levels. Recently, we introduced the continuous glucose-monitoring test (CGM) (Medtronic Minimed-CGMS System Gold). Here we describe our experience with this methodology over the year 2004. A total of 141 CGM tests were performed over this period of time. Overall, 88% (n= 124) patients were diabetics (DM), 99 of them were insulin users. We found a strong correlation between glucose values obtained by CGM and capillary glucose measures (r= 0.926; p< 0.005). In diabetic patients, nocturnal hypoglycemia (< 50 mg/dL) was identified in approximately 35% (n= 44), hyperglycemic patterns (> 220 mg/dL) at specific times of day in approximately 44% and sustained hyperglycemia throughout the whole monitoring period in thirteen cases (10%). Twelve tests were performed to investigate the occurrence of hypoglycemia in non-diabetic subjects. Two tests came out very suggestive of "dumping", and in one case the CGMS supported the hypothesis of insulinoma. Partial monitoring interruptions have occurred in 15% of all tests. We concluded that CGMS is a useful methodology to investigate glycemic fluctuations, and it is also an important tool to adjust therapy in diabetic patients.

Severe hypercalcemia in a 9-year-old Brazilian girl due to a novel inactivating mutation of the calcium-sensing receptor.

Familial hypocalciuric hypercalcemia (FHH) and neonatal severe hyperparathyroidism (NSHPT) are consequent to inactivating mutations of the calcium-sensing receptor (CaR) gene. FHH is usually associated with heterozygous inactivating mutations of the CaR gene, whereas NSHPT is usually due to homozygous inactivation of the CaR gene. FHH is generally asymptomatic and is characterized by mild to moderate lifelong hypercalcemia, relative hypocalciuria, and normal intact PTH, whereas individuals with NSHPT frequently show life-threatening hypercalcemia. In this study, we report a novel inactivating mutation of the CaR gene, identified in a 9-yr-old Brazilian girl who was found to be severely hypercalcemic during investigation of a 6-month history of headaches and vomits. Direct sequencing of the CaR gene from this patient showed a novel homozygous mutation (L13P) in exon 2. Functional characterization by intracellular calcium measurement by fluorometry showed that the mutant receptor had a dose-response curve shifted to the right relative to that of wild type. The proband's consanguineous parents, who had mild asymptomatic hypercalcemia, showed the same mutation in the heterozygous form. The mutation described in this study is the inactivating missense mutation present at the most N-terminal end among the known CaR missense mutations. This study reinforces the fact that patients with homozygous inactivation of the CaR gene may present with severe hypercalcemia in different phases of life.

[Free thyroxine values during pregnancy]. / Definição de valores normais de tiroxina livre durante a gravidez.

Pregnancy induces a series of physiological modifications that include a significant elevation of thyroxine-binding globulin (TBG) levels. This elevation interferes in the serum levels of total thyroxine and stresses the use of free thyroxine (FT4), together with TSH measurement, as the first line tests in the evaluation of thyroid function in pregnancy. A careful definition of the normal values for FT4 during pregnancy is paramount for the study of thyroid abnormalities, since minimal dysfunctions can result in significant fetal abnormalities. We studied 132 normal pregnant women, from 6 to 38 weeks of gestation, and the serum FT4 measured by an indirect two-step assay (normal values for non-pregnant women: 0.7 to 1.5 ng/dL; mean+/-SD 0.98+/-0.14 ng/dL, n= 797) showed values between 0.5 and 1.3 ng/dL; mean+/-SD of 0.78+/-0.16 ng/dL, values significantly lower than the observed in non-pregnant women (P<0.0001). Values tended to decline progressively throughout pregnancy, with a significant negative correlation with TBG levels (rs= -0.51, P<0.0001), as well as with weeks of gestation (rs= -0.649, P<0.0001). TSH levels did not show any correlation with gestational age. Our data corroborate the need of a precise definition of FT4 normal values during pregnancy, aiming a better laboratory evaluation of thyroid dysfunctions in this group of patients.

[Parathyroid hormone values obtained with immunometric assays depend on the amino-terminal antibody specificity]. / Valores de paratormônio obtidos com ensaios imunométricos dependem da especificidade do anticorpo amino terminal empregado.

Introduction of 2nd generation immunometric assays for the measurement of serum parathyroid hormone (PTH), turned them more available, simple and rapid. These methods, based on double identification of the PTH molecule, supposedly measure the intact, bioactive molecule, with the sequence 1-84. Recent works showed that they also measure forms with amino-terminal deletions, like the 7-84 form, which are not able to activate the traditional PTH receptor (PTH1R). Thus, an important practical aspect is the definition of the PTH forms measured by the immunometric assays, a fact that depends on the specificity of the antibodies employed. In this report we compare the results obtained with an in-house immunofluorometric assay that presents a cross-reactivity of 50% with the 7-84 PTH sequence, and two commercial 2nd generation assays, that react 100%. In a first study, 135 samples were measured using our assay and an electrochemiluminescent assay, resulting in a correlation coefficient of 0.961 (P<0.0001) and medians of 35.0 and 51.0 ng/L (P<0.0001). In a second study, 252 samples were analyzed using our assay and an immunochemiluminometric assay, resulting in a correlation of 0.883 (P<0.0001) and medians of 36.0 and 45.5 ng/L (P<0.0001). In both studies results obtained with the in-house assay were significantly lower, as expected by the specificity of the anti-amino-terminal antibody employed. Our data support the need of a precise description of the specificity of the amino-terminal antibodies employed in 2nd generation PTH assays in order to better compare results and define normal ranges.

Fasting insulin concentration is highly correlated with quantitative insulin sensitivity check index.

Given that the "gold standard" method for evaluating insulin sensitivity in vivo (hyperinsulinemic euglycemic glucose clamp technique) cannot be routinely applied because of technical reasons, simple methods and indexes were developed and are currently available to assess insulin sensitivity in vivo. Quantitative insulin sensitivity check index (QUICKI) has recently been described and is able to accurately estimate insulin sensitivity from a fasting blood sample. We demonstrated that fasting insulin levels strongly inversely correlated with QUICKI in three different groups: 215 healthy nondiabetic nonobese subjects, 62 nondiabetic obese subjects, and 44 patients with glucose intolerance or type 2 diabetes mellitus. Fasting insulin measurement is a simple way of assessing insulin sensitivity in obese and nonobese humans, with or without glucose intolerance or type 2 diabetes mellitus.

Screening for macroprolactinaemia and pituitary imaging studies.

OBJECTIVE: Hyperprolactinaemia is caused by high levels of monomeric, dimeric or macro forms of prolactin in circulation, the monomeric form being predominant in patients with prolactinomas. Macroprolactinaemia, however, is common and is associated with asymptomatic cases. In this study, we reviewed our records regarding clinical and imaging investigations in patients who were found to have hyperprolactinaemia predominantly due to the presence of macroprolactin and compared them with the findings observed in patients whose prolactin molecular size consisted predominantly of the monomeric form. PATIENTS AND METHODS: We conducted a retrospective study of 113 consecutive patients (nine men and 104 women, aged 19-67 years, median age 39 years) with hyperprolactinaemia who were screened for the presence of macroprolactin by polyethylene glycol precipitation and/or chromatography and submitted to pituitary magnetic resonance imaging (MRI) and/or computerized tomography (CT). RESULTS: Fifty-two of 113 patients (46%) had hyperprolactinaemia due to macroprolactin, whereas the remaining 61 patients (54%) had their hyperprolactinaemia confirmed by the predominance of the monomeric form. Both groups shared similar mean prolactin levels (79.9 +/- 63.6 micro g/l, median of 62.0 micro g/l, and 97.9 +/- 155.4 micro g/l, median of 61.0 micro g/l, respectively). Of the patients with macroprolactinaemia, 46% had no symptoms of hyperprolactinaemia, whereas only 10% of the patients who screened negative for macroprolactin were asymptomatic. There was an association between macroprolactinaemia and negative pituitary imaging findings: normal pituitary images were found in 78.9% of patients who had macroprolactinaemia and in 25% of patients with monomeric hyperprolactinaemia. In addition, none of the patients with macroprolactinoma (seven cases) had macroprolactinaemia. CONCLUSIONS: The presence of macroprolactinaemia does not exclude the possibility of a pituitary adenoma and consequently may not prevent pituitary imaging studies. However, our data demonstrate that all asymptomatic patients who screened positive for macroprolactin had normal pituitary imaging studies. Patient samples showing hyperprolactinaemia should be first tested for macroprolactin, before the patient is submitted to imaging studies. We suggest that imaging studies should be ordered in patients with macroprolactinaemia when indicated by clinically relevant features. As a result, unnecessary anxiety and costly medical procedures may be prevented.

Valores inesperadamente elevados de TSH: a presença de formas de alto peso molecular ("macro TSH") deve ser investigada / Unexpected high values of TSH: the presence of high molecular weight forms (macro TSH) must be investigated

As metodologias empregadas para a medida de TSH sérico apresentam níveis de especificidade e sensibilidade, tanto diagnósticas como analíticas, bastante elevadas. Adicionalmente, são metodologias bastante robustas, de maneira que resultados falso-positivos ou falso-negativos são raros e inesperados. Descrevemos neste trabalho dois casos de indivíduos descritos como eutiróideos, sem antecedentes de doenças autoimunes e sem referência ao uso de TSH exógeno, que apresentavam níveis de TSH de normais a muito elevados, dependendo da metodologia empregada. Em três métodos testados para a medida de TSH a diluição seriada das amostras mostrou que os níveis reais situavam-se entre 250 e 300 mUI/L. Nos dois casos, o aumento de TSH foi ocasionado pela presença de proteínas ligadoras de TSH no soro, formando formas de alto peso molecular ("macro TSH"), demonstradas por cromatografia de gel filtração em coluna de Superdex S-200. Em uma das pacientes a proteína ligadora foi caracterizada como IgG através de cromatografia em proteína G sepharose, na outra, a ligação em proteína G e em coluna de sepharose acoplada a monoclonal anti-IgM não conseguiu caracterizar a proteína ligadora sérica. Estes casos salientam a importância da correlação clínico-laboratorial e sugerem a necessidade de se pesquisar a presença de macro TSH em pacientes com níveis de TSH anormalmente elevados.

Carcinoma de paratiróide / Parathyroid carcinoma

Carcinoma de paratiróide é uma condição rara, correspondendo na maior parte das casuísticas a menos de 1 por cento dos casos de hiperparatiroidismo primário (HPP). No entanto, pela sua gravidade, e com o prognóstico dependente do diagnóstico precoce e de uma conduta agressiva, é fundamental que a suspeita clínica seja feita pré-operatoriamente. As características clínicas são compatíveis com um caso de HPP grave, sintomático, com tumor cervical >1,5cm, podendo ser palpável. A definição anátomo-patológica pode ser difícil em muitos casos. Nossa casuística (1983-2004) compreende 7 casos, todos sintomáticos, com síndrome hipercalcêmica e doença óssea presente na maioria. Em 6/7 o tumor era palpável, e todos apresentavam quadro bioquímico compatível. Três pacientes faleceram em quadro de hipercalcemia refratária. Dados recentes apontam para uma mutação no gene HRPT2 como base molecular para o desenvolvimento destes tumores. A conduta é cirúrgica e deve incluir hemitiroidectomia e exploração cervical ampliada, procurando focos metastáticos. O pós-operatório é compatível com a gravidade da alteração metabólica pré-existente, sendo comum a tendência a hipocalcemia. O prognóstico de longo prazo depende do diagnóstico precoce, do sucesso cirúrgico e do controle da hipercalcemia. Novas possibilidades terapêuticas, na forma de bisfosfonatos e drogas calcimiméticas, bem como a possibilidade de diagnóstico genético, tendem a melhorar o prognóstico desta grave condição.

Tolerância ao teste da clonidina em 180 pacientes: estudo da eficácia da expansão volêmica para o controle de hipotensão arterial / Tolerance of the oral clonidine test in 180 patients: efficacy of saline resuscitation in controlling arterial hypotension

O teste da clonidina é amplamente usado para avaliar a secreção do hormônio do crescimento. Os efeitos colaterais são sonolência (35 por cento) e hipotensão arterial (HA) (5 por cento). Nossos objetivos foram avaliar a tolerância ao teste quanto à queda da pressão arterial (PA), grau de sedação e eficácia da expansão volêmica para controle da HA. A PA foi medida nos tempos basal, 60 e 120 min. A sedação foi baseada na escala Ramsay. Os pacientes foram divididos em dois grupos: o Grupo 1 (n= 80) recebeu expansão volêmica apenas com HA grave (queda da PA média [PAM] > 20 por cento da PAM inicial) e/ou hipotensão postural; o Grupo 2 (n=100) recebeu expansão volêmica desde o início do teste. Nos dois grupos, a PAM caiu significativamente e 75 por cento apresentaram sonolência aos 60 min. Não houve correlação da queda da PAM com grau de sedação e dose administrada. O Grupo 1 apresentou mais hipotensão (59 por cento x 28 por cento) e maior queda da PAM aos 60 min. Apenas um paciente apresentou broncoespasmo. Concluímos que o efeito hipotensor da clonidina diminui com expansão volêmica desde o início no teste. Este teste deve ser sempre feito com acompanhamento médico especializado para observação estrita da PA e intervenção precoce, se necessária.

Monitorização contínua de glicose: análise crítica baseada em experiência ao longo de um ano / Continuous glucose monitoring: a critical appraisal after one year experience

A avaliação do controle glicêmico no diabetes mellitus (DM) envolve tradicionalmente a observação das taxas de glicemia e hemoglobina glicada. Recentemente o Fleury - Centro de Medicina Diagnóstica implantou o exame de monitorização contínua de glicose (MCG) (Medtronic Minimed - CGMS® System GoldTM) e, neste trabalho, objetivamos descrever a experiência relacionada à realização deste exame durante o ano de 2004. Realizaram-se 141 exames neste período. Do total, 88 por cento (n= 124) pacientes eram diabéticos, sendo 99 usuários de insulina. Encontramos forte correlação entre os valores de glicose obtidos com a MCG e no sangue capilar (r= 0,926; p< 0,005). Nos diabéticos, identificou-se hipoglicemia noturna (< 50mg/dL) em 35 por cento (n= 44), padrões hiperglicêmicos (> 220mg/dL) em períodos determinados do dia em 44 por cento e hiperglicemia sustentada ao longo de toda monitorização em treze casos (10 por cento). Doze exames foram realizados para investigação de hipoglicemias em não diabéticos. Dois exames foram sugestivos de "dumping" e em um caso a MCG reforçou a hipótese de insulinoma. Ocorreram interrupções parciais das monitorizações em 15 por cento dos exames. Concluímos que a MCG é uma metodologia útil para investigação das oscilações glicêmicas, sendo uma importante ferramenta para ajuste terapêutico em pacientes com DM.

Diagnóstico laboratorial do carcinoma medular de tiróide: calcitonina basal e testes de estímulo / Biochemical diagnosis of medullary thyroid carcinoma: basal calcitonin and provocative tests

A calcitonina é um hormônio secretado pelas células parafoliculares tiroideanas. O diagnóstico de carcinoma medular de tiróide (CMT) pode ser suspeitado a partir do encontro de níveis aumentados de calcitonina basal ou após testes de estímulos específicos. Neste sentido, a calcitonina caracteriza-se como um importante marcador tumoral para o diagnóstico e seguimento de pacientes portadores de CMT. Neste artigo, revisamos alguns tópicos referentes à utilidade da dosagem de calcitonina basal em pacientes portadores de nódulos de tiróide para rastreamento de CMT. Comentamos a respeito dos principais testes de estímulo para secreçäo de calcitonina disponíveis e finalizamos com algumas observações sobre os ensaios para dosagem de calcitonina.