Pyridostigmine Effects on Tsh Response to Trh in Adult and Children Obese Subjects

Thyrotropin releasing hormone (TRH) administration is known to induce a greater TSH response in normal subjects than in obese subjects. In obesity even GH and PRL response to various stimuli are blunted, presumably because of an augmented somatostatinergic tone in obese subjects. Further studies have shown that pyridostigmine (Pyr), an acetylcholinesterase inhibitor, is capable of augmenting GH in obesity by means of somatostatin inhibition. In order to evaluate the possible interference of an increased somatostatinergic tone on TSH secretion, we studied the TSH response to a TRH bolus in 5 obese children with or without a pyr pretreatment. Similarly, we tested a group of 10 obese adult subjects, with TRH alone or TRH plus pyr administration, 30 min or 60 min before TRH. All subjects had a body weight of 30-50% greater than I.B.W. Our data show that a pretreatment with pyr, 60 min before TRH administration, significantly augments the TSH response in adult obese subjects but not in children; the modality of pyr administration seems to be crucial to evidenciate such an alteration since the pyr pretreatment is not effective when administered 30 min before TRH. The absence of this pyr effect in obese children induces to hypothesize that somatostatinergic tone is differentially modulated in children vs adult obese subjects.