Long-term intramuscular administration of thyrotropin-releasing hormone tartrate in patients with cerebrovascular disease: effects on the pituitary-thyroid axis.
We studied the effects of long-term (30 days) refracted daily intramuscular administration of 4 mg TRH tartrate (TRH-T) on the pituitary-thyroid axis in 20 euthyroid patients affected by cerebrovascular disease (CVD). All subjects were assayed for T4, T3, FT4, FT3, TSH and TBG plasma levels before treatment (D0), after 15 and 30 treatment days (D15, D30), and after a 15-day washout (D45). In addition, TSH response to 200 micrograms intravenous TRH was assessed at D0, D30 and D45. We observed a significant increase in T4, FT4 and FT3 levels in the face of decreased TSH concentrations. A blunted TSH response to TRH bolus persisted at D30. These data demonstrate that the down-regulation mechanism may be partially overcome in vivo when thyrotrophs are chronically exposed to pharmacological TRH-T doses and that TSH pattern is mainly due to the negative feedback of thyroid hormones, even though pituitary TSH reserves may become depleted. Furthermore, prolonged TRH-T administration does not produce hyperthyroidism in euthyroid CVD patients.
Monzani
F
F
Clinica Medica II, Università di Pisa, Italia.
Pucci
E
E
Fierabracci
P
P
Nebbiai
G
G
Coli
A
A
Caraccio
N
N
De Negri
F
F
Franchi
F
F
Baschieri
L
L
D000368:Aged; D002561:Cerebrovascular Disorders / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007273:Injections, Intramuscular; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D013954:Thyroglobulin / Q000097:blood; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage / Q000627:therapeutic use*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D013954:Thyroglobulin; D013974:Thyroxine