title: [Variations in the serum levels of thyroid hormones and TSH after intake of a dose of L-thyroxine in euthyroid subjects and in adequately-treated hypothyroid patients].
abstract: The aim of the present study was to determine whether the temporary variations in blood thyroid hormone levels secondary to a therapeutic dose administration of L-thyroxine observed in adequately treated hypothyroid patients also occur in spontaneously euthyroid subjects under analogous conditions. Serum levels of T3, T4, FT3, FT4 and TSH were measured over 6 hours following a single oral administration of L-thyroxine (dosage 85 mcg/mq body surface area) in a group of 18 euthyroid volunteers and 8 hypothyroid patients adequately compensated with replacement therapy. In the euthyroid subjects there was a significant increase in T4 and a significant fall in TSH values at 60', while a significant decrease in FT3 and FT4 as compared to initial values was observed at 120'. In the treated hypothyroid patients serum T3 and T4 increased at 120', while FT4 concentrations, already significantly higher at 120', still remained higher than initial levels at 360'. The different behaviour of the hypothyroid patients, in spite of being compensated with therapeutic doses of L-thyroxine, reflects the persistence of a thyroid-metabolic condition substantially different to the physiological feature, which appears to be realized by means of a reduced iodothyronine clearance and a lower sensitivity in TSH feedback.
authors.forename: N
authors.initials: N
authors.lastname: Custro
authors.forename: V
authors.initials: V
authors.lastname: Scafidi
authors.forename: G
authors.initials: G
authors.lastname: Costanzo
authors.forename: F P
authors.initials: FP
authors.lastname: Corsello
mesh_terms: D000284:Administration, Oral; D000328:Adult; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood*; D008297:Male; D008875:Middle Aged; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D013963:Thyroid Hormones; D013972:Thyrotropin; D013974:Thyroxine
vernacular_title: Variazioni dei livelli sierici degli ormoni tiroidei e del TSH dopo assunzione di una dose di L-tiroxina in soggetti eutiroidei e in pazienti ipotiroidei adeguatamente trattati.