. *
0021-972X/78/4703-0689$02.00/0 Journal of Clinical Endocrinology and Metabolism Copyright © 1978 by The Endocrine Society
Vol. 47, No. 3 Printed in U.S.A.
Effect of Pyridoxine on Pituitary Release of Growth Hormone and Prolactin in Childhood and Adolescence* EDWARD O. REITER AND ALLEN W. ROOT Department of Pediatrics, University of South Florida College of Medicine, Tampa; and the Ed Wright Pediatric Endocrine Research Laboratory, All Children's Hospital, St. Petersburg, Florida ABSTRACT. The dopamine agonist, pyridoxine, was administered to 10 children being evaluated for short stature. Serum GH and PRL responses were contrasted to those after insulin-induced hypoglycemia (ITT) and L-dopa administration. Levels of GH did not change after pyridoxine, but PRL fell (P < 0.05) to 42% of the
zero time concentration. Significant increments of GH occurred during ITT and after L-dopa, while PRL was suppressed to a greater extent by L-dopa. We conclude that pyridoxine is not useful in assessment of hypothalamic-pituitary function. (JClin Endocrinol Metab 47: 689, 1978)
YRIDOXINE may facilitate the neural and peripheral decarboxylation of L-dopa to dopamine (1) and thus increase dopaminergic activity. Delitala et al (2) reported a significant increment in plasma concentrations of GH and a decrement in PRL levels after bolus iv administration in normal adults. L-Dopa, frequently used to evaluate GH secretion in short children (3, 4), is often associated with nausea and vomiting. As a test utilizing dopaminergic stimulation of GH seems desirable, we have administered pyridoxine to normal short children and compared GH and PRL responses to those elicited during insulininduced hypoglycemia and after L-dopa administration.
saline was established in a peripheral vein. After a 30-min period of equilibration, 0.10 U/kg regular crystalline insulin (ITT) or 300 mg pyridoxine were administered by bolus iv injection or 250-500 mg L-dopa was ingested (4). All of the patients had the three different tests; the ITT-L-dopa test was done in a sequential manner, the pyridoxine test was performed on a separate day. Samples, collected serially between —30 and +150 min, were centrifuged and the sera were separated and stored at —20 C. Serum GH and PRL concentrations were determined by double antibody RIAs. Individuals who achieve GH levels of >5 ng/ml in this assay were considered to have adequate pituitary secretion of GH (5). Standard statistical techniques were used to analyze the data.
Materials and Methods
The serum concentrations of GH after administration of iv pyridoxine did not change significantly [peak concentration, 2.4 ± 0.3 (SE) ng/ml; Table 1]. GH levels rose significantly (P < 0.01) both during insulin-induced hypoglycemia (peak concentration, 9.1 ± 1.9) and also after ingestion of L-dopa (13.2 ± 2.3). PRL levels gradually fell after pyridoxine from a zero value of 22.3 ± 5.1 to a mean nadir (to +90 min) of 9.3 ± 3.4 (P < 0.05, paired t test). Similarly, PRL concentrations fell (P < 0.01) from 18.3 ± 4.4 to a nadir of 5.0 ± 1.5 after L-dopa administration. No consistent changes in concentrations of PRL were observed during insulin-induced hypoglycemia.
P
Results
Subjects Ten children (eight males and two females; 8-17 yr) without evidence of systemic or endocrinologic disease were evaluated for short stature. Procedures After an overnight fast, an iv infusion of isotonic Received November 21, 1977. Address requests for reprints to: Dr. Edward 0. Reiter, All Children's Hospital, 801 Sixth Street South, St. Petersburg, Florida 33701. * This work was supported by the National Foundation-March of Dimes Grants 1-323 and C-199 and Basil O'Connor Starter Grant 5-71.
689
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 25 September 2015. at 18:20 For personal use only. No other uses without permission. . All rights reserved.
690
JCE&M • 1978 VoU7 • No 3
COMMENTS
TABLE 1. Effects of pyridoxine on GH and PRL in children Time Patient no. -30 min GH (ng/ml) 1 2 3 4
0 min
+30 min
60 min
90 min
120 min
0021-972X/78/4703-0689$02.00/0 Journal of Clinical Endocrinology and Metabolism Copyright © 1978 by The Endocrine Society
Vol. 47, No. 3 Printed in U.S.A.
Effect of Pyridoxine on Pituitary Release of Growth Hormone and Prolactin in Childhood and Adolescence* EDWARD O. REITER AND ALLEN W. ROOT Department of Pediatrics, University of South Florida College of Medicine, Tampa; and the Ed Wright Pediatric Endocrine Research Laboratory, All Children's Hospital, St. Petersburg, Florida ABSTRACT. The dopamine agonist, pyridoxine, was administered to 10 children being evaluated for short stature. Serum GH and PRL responses were contrasted to those after insulin-induced hypoglycemia (ITT) and L-dopa administration. Levels of GH did not change after pyridoxine, but PRL fell (P < 0.05) to 42% of the
zero time concentration. Significant increments of GH occurred during ITT and after L-dopa, while PRL was suppressed to a greater extent by L-dopa. We conclude that pyridoxine is not useful in assessment of hypothalamic-pituitary function. (JClin Endocrinol Metab 47: 689, 1978)
YRIDOXINE may facilitate the neural and peripheral decarboxylation of L-dopa to dopamine (1) and thus increase dopaminergic activity. Delitala et al (2) reported a significant increment in plasma concentrations of GH and a decrement in PRL levels after bolus iv administration in normal adults. L-Dopa, frequently used to evaluate GH secretion in short children (3, 4), is often associated with nausea and vomiting. As a test utilizing dopaminergic stimulation of GH seems desirable, we have administered pyridoxine to normal short children and compared GH and PRL responses to those elicited during insulininduced hypoglycemia and after L-dopa administration.
saline was established in a peripheral vein. After a 30-min period of equilibration, 0.10 U/kg regular crystalline insulin (ITT) or 300 mg pyridoxine were administered by bolus iv injection or 250-500 mg L-dopa was ingested (4). All of the patients had the three different tests; the ITT-L-dopa test was done in a sequential manner, the pyridoxine test was performed on a separate day. Samples, collected serially between —30 and +150 min, were centrifuged and the sera were separated and stored at —20 C. Serum GH and PRL concentrations were determined by double antibody RIAs. Individuals who achieve GH levels of >5 ng/ml in this assay were considered to have adequate pituitary secretion of GH (5). Standard statistical techniques were used to analyze the data.
Materials and Methods
The serum concentrations of GH after administration of iv pyridoxine did not change significantly [peak concentration, 2.4 ± 0.3 (SE) ng/ml; Table 1]. GH levels rose significantly (P < 0.01) both during insulin-induced hypoglycemia (peak concentration, 9.1 ± 1.9) and also after ingestion of L-dopa (13.2 ± 2.3). PRL levels gradually fell after pyridoxine from a zero value of 22.3 ± 5.1 to a mean nadir (to +90 min) of 9.3 ± 3.4 (P < 0.05, paired t test). Similarly, PRL concentrations fell (P < 0.01) from 18.3 ± 4.4 to a nadir of 5.0 ± 1.5 after L-dopa administration. No consistent changes in concentrations of PRL were observed during insulin-induced hypoglycemia.
P
Results
Subjects Ten children (eight males and two females; 8-17 yr) without evidence of systemic or endocrinologic disease were evaluated for short stature. Procedures After an overnight fast, an iv infusion of isotonic Received November 21, 1977. Address requests for reprints to: Dr. Edward 0. Reiter, All Children's Hospital, 801 Sixth Street South, St. Petersburg, Florida 33701. * This work was supported by the National Foundation-March of Dimes Grants 1-323 and C-199 and Basil O'Connor Starter Grant 5-71.
689
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 25 September 2015. at 18:20 For personal use only. No other uses without permission. . All rights reserved.
690
JCE&M • 1978 VoU7 • No 3
COMMENTS
TABLE 1. Effects of pyridoxine on GH and PRL in children Time Patient no. -30 min GH (ng/ml) 1 2 3 4
0 min
+30 min
60 min
90 min
120 min
