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Effect of prolonged intermittent thyrotropin-releasing hormone administration to fetal and neonatal rats
Insights
Perinatal exposure to thyrotropin-releasing hormone (TRH) does not impact the adult hypothalamo-pituitary axis in rats. Repeated TRH administration during development did not alter thyroid hormone levels or TSH response to challenges in adulthood.
Area of Science:
- Endocrinology
- Neuroscience
- Developmental Biology
Background:
- The hypothalamo-pituitary-thyroid axis regulates metabolism and development.
- Perinatal exposure to hormones can have long-lasting effects on endocrine function.
Purpose of the Study:
- To investigate the long-term effects of perinatal thyrotropin-releasing hormone (TRH) exposure on the hypothalamo-pituitary axis in rats.
- To determine if early-life TRH administration alters adult thyroid hormone regulation and thyroid-stimulating hormone (TSH) response.
Main Methods:
- Fetal and neonatal rats received daily subcutaneous injections of 10 microgram TRH.
- Animals were challenged intravenously with TRH at 70 days of age.
- Basal and stimulated serum levels of thyroxine, triiodothyronine, and TSH were measured, along with pituitary TSH content.
Main Results:
- No significant differences were observed in basal serum thyroxine, triiodothyronine, or TSH concentrations among the groups.
- The mean peak TSH concentration and total TSH response following TRH challenge did not differ significantly.
- Pituitary TSH content remained unchanged after the TRH challenge in all groups.
Conclusions:
- Repeated administration of pharmacologic doses of TRH during the perinatal period does not affect the integrity of the hypothalamo-pituitary axis in adult rats.
- Early-life TRH exposure does not appear to permanently alter thyroid hormone homeostasis or the TSH feedback mechanism.
Abstract:
Fetal and neonatal rats received daily subcutaneous injections of 10 microgram thyrotropin-releasing hormone (TRH) until 7 or 14 days postnatally. At 70 days the pups were challenged with 1 microgram TRH intravenously via an indwelling jugular cannula. Basal serum thyroxine, triiodothyronine, and thyroid-stimulating hormone (TSH) concentrations did not differ among the three groups. The mean TSH responses as determined by the mean peak TSH concentration and the total TSH response as determined by planimetry were not significantly different, and there was no significant difference in pituitary TSH content following the TRH challenge among the three groups. This study suggests that the integrity of the hypothalamo--pituitary axis in adult rats cannot be affected by the repeated administration of pharmacologic doses of TRH during the perinatal period.