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Biomedical subjects

P J Howanitz

Publications and source records attributed to P J Howanitz.

83 records · Page 5Linked to original sources
PubMed1982

Incidence and mechanism of spurious increase in serum thyrotropin.

We previously reported spuriously high values for thyrotropin (TSH), presumably owing to an antibody in human serum that reacts with both reagent rabbit antibodies in an immunoradiometric assay (IRMA). We used this IRMA to measure TSH. Five of 20 sera from laboratory animal handlers showed spuriously high values. When we added 2 mL of nonimmune rabbit serum per liter to the labeled IRMA rabbit antibody reagent and reassayed the five affected specimens, the results were within the reference interval. Smaller additions partly corrected the TSH values, but nonimmune sera of eight other species had no effect. Substitution of goat solid-phase antibody decreased, but did not eliminate, the increases in TSH in three of the five affected sera. Chromatographic properties, results of rheumatoid factor testing, and measurement of human anti-rabbit immunoglobulin suggest that the interference is ascribable to an antibody of the IgG class that reacts with rabbit antibody. Evidently, antibody interference with IRMA procedures may be common in certain populations. It can be avoided by including nonimmune serum corresponding to the species used to produce reagent antibody.

Animals↗
PubMed1981

Iron sufficiency with prolonged exclusive breast-feeding in Peruvian infants.

Serum ferritin and erythrocyte porphyrin concentrations were measured in seven Peruvian infants, who ranged in age from 7.5-12.0 months (mean: 9.3 months), who had been exclusively breast-fed all their lives. No infant had evidence of iron deficiency as reflected by a reduced serum ferritin, or an increased erythrocyte porphyrin. Mean serum ferritin and erythrocyte porphyrin values in these seven infants were similar to those of 40 nonanemic, noniron-deficient U.S. infants who ranged in age from 9 to 12 months, on a mixed diet. These findings illustrate that exclusively breast-feeding an infant for at least 9 months of life meets the iron requirements of the full-term infant.

Breast Feeding↗
PubMed1981

Day-to-day variation in serum ferritin concentration in healthy subjects.

We report our observations on day-to-day variation in serum ferritin, serum iron, total iron-binding capacity, and percent saturation of binding proteins with iron in 13 ostensibly healthy subjects during five weeks. The average intrasubject coefficients of variation were 14.5, 28.5, 4.8, and 28.0%, respectively. Precision studies on control samples showed greater within-assay and between-assay analytical variation for serum ferritin than for serum iron or total iron-binding capacity. Evidently, serum ferritin varies less in a given individual from day to day than do serum iron and percent iron saturation. Thus, a single measurement of serum ferritin may be a more reliable index of iron stores than an isolated determination of either serum iron or percent iron saturation.

Adult↗
PubMed1976

Absence of nocturnal elevation of plasma prolactin concentrations in Cushing's disease.

The mean prolactin concentration during sleep and the per cent change (increase) and increment in the nocturnal elevation of plasma prolactin concentrations were significantly reduced (P less than .01, less than .01, and less than .001, respectively) in 6 untreated patients with clinically active Cushing's disease, compared with concentrations seen in normal subjects. There was no significant difference between mean-awake and mean-sleep plasma prolactin concentration in these patients, in contrast to that seen in normal subjects. In contrast, patients with hypercorticism secondary to adrenal adenoma (n = 2) or receiving long-term, high-dose corticosteroid therapy (n = 6) did not differ significantly from normal subjects in the percentage change seen in the nocturnal elevation of their plasma prolactin concentrations. Although mean prolactin concentration during sleep was reduced in these two categories of hypercorticism, a significant difference was still present between mean-awake and mean-sleep plasma prolactin concentration. (The nocturnal increment in plasma prolactin concentrations in these patients with hypercorticism compared with that of normal subjects was reduced, P less than .02). The difference between the percentage change and nocturnal increment observed in patients with Cushing's disease versus that seen in these two categories of hypercorticism was significant at P less than .02 and P less than .01, respectively. Four untreated patients with localized hypothalamic tumors also showed a significant reduction in the percentage change and increment in the nocturnal elevation of plasma prolactin concentrations (P less than .05 and P less than .02). In contrast to these findings, the prolactin responses to thyrotropin-releasing hormone (indicative of pituitary responsiveness) in patients with Cushing's disease, patients with adrenal adenoma, or those receiving chronic corticosteroid therapy, were all within the normal range seen in sex-matched control subjects. These findings provide additional evidence for the suggestion that there is altered hypothalamic function in patients with Cushing's disease.

Adrenal Cortex Hormones↗