The effects of intranasally sprayed synthetic TRH on TSH and on PRL secretion in children

The effects of intranasally applied TRH on serum TSH and PRL were investigated in ten healthy, prepubertal children. Serum levels of T4, T3, TSH, and PRL were all in the normal range. Synthetic TRH, 500 micrograms, in water was insufflated in one nostril. Intranasal TRH induced a prompt rise of TSH and PRL in all children with peak values at 30 min. TSH: 10.29 +/- 1.24 microU/ml; PRL: 25.12 +/- 3.53 ng/ml (mean +/- SEM). TSH values were still significant raised 120 min after the insufflation (P less than 0.025) whereas the PRL values did not differ significantly. A dose-dependent TSH release following intranasal sprayed TRH was shown. delta TSH and TSH values at 120 min were significantly higher in children receiving greater than 10 micrograms/kg TRH than in children receiving less than 10 micrograms/kg (P less than 0.025; P less than 0.05). Dose dependent differences in PRL release following intranasal TRH were not shown. Any side effects of intranasally applied TRH were not observed. Intranasal insufflation of synthetic TRH seems to be a valuable and harmless tool for the evaluation of pituitary TSH and PRL secretory reserve.