The effect of sun exposure on 25-hydroxyvitamin D concentrations in young healthy subjects living in the city of São Paulo, Brazil

The range of 25-hydroxyvitamin D (25OHD) concentration was determined in a young healthy population based on bone metabolism parameters and environmental and behavioral aspects. We studied 121 healthy young volunteers (49 men, 72 women) living in São Paulo (23º 34' south latitude) belonging to three occupational categories: indoor workers (N = 28), medical school students (N = 44), and resident physicians (N = 49). Fasting morning blood samples were collected once from each volunteer from August 2002 to February 2004, and 25OHD, total calcium, albumin, alkaline phosphatase, phosphorus, creatinine, intact parathyroid hormone, osteocalcin, and type I collagen carboxyterminal telopeptide were measured. Data are reported as means ± SD. Mean subject age was 24.7 ± 2.68 years and mean 25OHD level for the entire group was 78.7 ± 33.1 nM. 25OHD levels were lower (P < 0.05) among resident physicians (67.1 ± 27.0 nM) than among students (81.5 ± 35.8 nM) and workers (94.0 ± 32.6 nM), with the last two categories displaying no difference. Parathyroid hormone was higher (P < 0.05) and osteocalcin was lower (P < 0.05) among resident physicians compared to non-physicians. Solar exposure and frequency of beach outings showed a positive association with 25OHD (P < 0.001), and summer samples presented higher results than winter ones (97.8 ± 33.5 and 62.9 ± 23.5 nM, respectively). To define normal levels, parameters such as occupational activity, seasonality and habits related to solar exposure should be taken into account. Based on these data, we considered concentrations above 74.5 nM to be desired optimal 25OHD levels, which were obtained during the summer for 75 percent of the non-physicians.

Changes in clinical and laboratory findings at the time of diagnosis of primary hyperparathyroidism in a University Hospital in São Paulo from 1985 to 2002

In contrast to most developed countries, most patients with primary hyperparathyroidism in Brazil are still symptomatic at diagnosis. However, we have been observing a change in this pattern, especially in the last few years. We evaluated 104 patients, 77 females and 27 males aged 11-79 years (mean: 54.4 years), diagnosed between 1985 and 2002 at a University Hospital. Diagnosis was made on the basis of clinical findings and of high total and/or ionized calcium levels, high or inappropriate levels of intact parathyroid hormone and of surgical findings in 80 patients. Patients were divided into three groups, i.e., patients diagnosed from 1985 to 1989, patients diagnosed from 1990 to 1994, and patients diagnosed from 1995 to 2002. The number of new cases diagnosed/year increased from 1.8/year in the first group to 6.0/year in the second group and 8.1/year in the third group. The first group comprised 9 patients (mean serum calcium ± SD, 13.6 ± 1.6 mg/dl), 8 of them (88.8 percent) defined as symptomatic. The second group comprised 30 patients (mean calcium ± SD, 12.2 ± 1.63 mg/dl), 22 of them defined as symptomatic (73.3 percent). The third group contained 65 patients (mean calcium 11.7 ± 1.1 mg/dl), 34 of them symptomatic (52.3 percent). Patients from the first group tended to be younger (mean ± SD, 43.0 ± 15 vs 55.1 ± 14.4 and 55.7 ± 17.3 years, respectively) and their mean serum calcium was significantly higher (P < 0.05). All of symptomatic patients independent of group had higher serum calcium levels (12.4 ± 1.53 mg/dl, N = 64) than asymptomatic patients (11.4 ± 1.0 mg/dl, N = 40). Our data showed an increase in the percentage of asymptomatic patients over the years in the number of primary hyperparathyroidism cases diagnosed. This finding may be due to an increased availability of diagnostic methods and/or to an increased awareness about the disease.

Usefulness of a rapid immunometric assay for intraoperative parathyroid hormone measurements

Intraoperative parathyroid hormone (IO-PTH) measurements have been proposed to improve operative success rates in primary, secondary and tertiary hyperparathyroidism (PHP, SHP and THP). Thirty-one patients requiring parathyroidectomy were evaluated retrospectively from June 2000 to January 2002. Sixteen had PHP, 7 SHP and 8 THP. Serum samples were taken at times 0 (before resection), 10, 20 and 30 min after resection of each abnormal parathyroid gland. Samples from 28 patients were frozen at -70ºC for subsequent tests, whereas samples from three patients were tested while surgery was being performed. IO-PTH was measured using the Elecsys immunochemiluminometric assay (Roche, Mannheim, Germany). The time necessary to perform the assay was 9 min. All samples had a second measurement taken by a conventional immunofluorimetric method. We considered as cured patients who presented normocalcemia in PHP and THP, and normal levels of PTH in SHP one month after surgery and who remained in this condition throughout the follow-up of 1 to 20 months. When rapid PTH assay was compared with a routine immunofluorimetric assay, excellent correlation was observed (r = 0.959, P < 0.0001). IO-PTH measurement showed a rapid average decline of 78.8 percent in PTH 10 min after adenoma resection in PHP and all patients were cured. SHP patients had an average IO-PTH decrease of 89 percent 30 min after total parathyroidectomy and cure was observed in 85.7 percent. THP showed an average IO-PTH decrease of 91.9 percent, and cure was obtained in 87.5 percent of patients. IO-PTH can be a useful tool that might improve the rate of successful treatment of PHP, SHP and THP

Circulating forms of parathyroid hormone detected with an immunofluorometric assay in patients with primary hyperparathyroidism and in hyperparathyroidism secondary to chronic renal failure

In patients with uremia, intact parathyroid hormone (PTH) measurement appears to overestimate the biologically active hormone in circulation. The recent description of the accumulation in these patients of a non-intact PTH form measured by the standard immunometric assays, re-opened the question. In this study we submitted serum samples from 7 patients with primary hyperparathyroidism (PHP) and from 10 patients with hyperparathyroidism secondary to chronic renal failure (SHP) to preparative HPLC in order to discriminate the molecular forms measured by our currently used immunofluorometric assay for intact PTH. The elution profile obtained with the HPLC system showed two clearly defined peaks, the first one corresponding to a lower molecular weight form, and the second to the intact PTH (1-84) form. In patients with SHP the area under the curve for the first peak (mean 29.5 percent, range 20.6 to 40.4 percent) was significantly greater than that observed for patients with PHP (mean 15.6 percent, range 5.6 to 21.9 percent). This confirms previous studies showing accumulation of molecular forms of slightly lower molecular weight, presumably PTH (7-84), in patients with SHP and, to a lesser extent, in patients with PHP. The real necessity of assays that discriminate between these two molecular forms is debatable

Comparaçäo entre duas estratégias para a detecçäo precoce do hipotireoidismo congênito / Comparison between two strategies for the precocious detection of congenital hypothyroidism

Objetivo. Comparar em recém-nascidos (RN) duas estratégias diferentes para o rastreamento do hipotiroidismo congênito (HC), a dosagem primária de TSH no sangue colhido do cordao umbilical (método 1) e a dosagem primária de T4 no sangue colhido por punçao de calcanhar no 2 dia de internaçao (método 2). Métodos. Os autores compararam as duas estratégias em 10.000 RN. Dosaram o TSH por método imunofluorimétrico sensível em papel de filtro e o T4 por radioimunoensaio em papel de filtro. A coleta de sangue do calcanhar foi realizada no 2 dia de vida. Resultados. Os dois programas diagnosticaram todos os casos de HC nos RN (4 casos, 1/2.500 RN). O índice de rechamada por coleta inadequada foi nulo no método 1 e de 8,5 por cento (850RN) no método 2. O índice de reconvocaçao para confirmaçao de resultados foi de 0,06 por cento (6RN) no método 1 e 2,25 por cento (225 RN) no método 2; quando este método incluía também a dosagem suplementar de TSH, o índice baixou para 1,63 por cento (163 RN). Conclusao. Os dados dos autores evidenciam a superioridade técnica da coleta de sangue a partir do cordao umbilical em relaçao à punçao de calcanhar, assim como da dosagem primária de TSH em relaçao à de T4, uma vez que apresentam índices muito menores de reconvocaçao.

Enzyme-linked thyroglobulin immunoassay

A one-step enzyme linked sandwich immunoassay using Silicone rods coated with rabbit anti-human thyroglobulin anti-Tg) immunoglobulin G (Fab') conjugated with beta-D-galactosidase was established for the measurement of thyroglobulin in human sera. The volume of serum needed for the assay was 2 mul The sensitivity of the assay was 1.52 amol/tube, corresponding to O.5 ng/ml. The precision was proven by coefficients of variation: intra-assay, 7.0 to 9.1 per cent: inter-assay, 5.3 to 7.4 per cent. The correlation between this EIA and RIA was O.91, p < O.O1.

An enzymeimmunoassay for the determination of thyrotropin (TSH) in drieb blood on filter paper: application to a screening program for detection of congenital hypothyroidism

An enzymeimmunoassay (EIA) for H-TSH (human thyrotropin) in dried blood on filter paper using an anti-H-TSH conjugate with ß-D-galactosidase and tubes coated with an anti-H-TSH was performed fo the screening program for detection of congenital hypothyroidism. The blood volume needed in this assay was 8.7 µl. The precision was evaluated by coefficients of variance within and between assays: 11.86 percent and 14.36 percent for H-TSH levels of 18.5 µU/ml and 35 µU/ml. A good correlation was observed between H-TSH concentration measured by EIA and RIA (r=0.91)

Development and clinical application of an immunoflurometric assay for intact parathyroid hormone

Parathyroid hormone (PTH) is a linear peptide of 84 amino acids that is found in serum mainly in the form of carboxyl-terminal fragments. The biological activity of PTH depends on the presence of the amino-terminal portion and in circulation is limited to the intact molecule. We describe an immunmofluorometric assay for the measurement of PTH-(1-84) based on a chicken egg yolk-derived amino-terminal antibody bound to microtiter plates by an anti-chicken Ig monoclonal antibody. As tracer antibody we employed a Europium-labelled carboxyl-terminal specific monoclonal antibody produced from a mouse immunized with hPTH-(53-84)-BSA conjugate. The assayincluded an initial overnight incubation of the sample and the solid phase-bound amino-terminal antibody, followed by washing and addition of the tracer antibody, and an additional two hours of incubation prior to fluorescence reading. The least-detectable dose was in the order of 2.5 pg/.ml and preliminary studies in 40 normal adults showed values in the range of 4 to 70 pg/ml; fo 12 patients with surgery-proven primary hyperparathyroidism values ranged from 109 to 743 pg/ml and for 34 patients with humoral hypercalcemia of malignancy from 2.5 to 66 pg/ml. We conclude that this assay, with its increased sensitivity and specificity, will be a valuable tool in the study of PTH secretion in normal and pathological situations