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The plasma GH, PRL, TSH, and dopamine (DA) responses to an infusion of L-dopa were examined in six acromegalic patients before and after pretreatment with carbidopa, a drug which inhibits the peripheral conversion of L-dopa to DA. Carbidopa neither modified baseline DA nor induced changes in baseline GH, PRL, or TSH levels. The drug instead markedly reduced the L-dopa-induced DA rise, an effect which was concomitant to a striking reduction of the suppressive effect of L-dopa on plasma GH and a partial inhibition of the suppressive effect of L-dopa on plasma PRL. TSH levels did not change either after L-dopa alone or L-dopa plus carbidopa. These data demonstrate that in "responder" acromegalics, L-dopa inhibits GH secretion through its peripheral conversion to DA and not via activation of central DA neurotransmission. For the effect of L-dopa on PRL secretion, in addition to a peripheral dopaminergic component, a central component cannot be disregarded.
F Camanni, and
G B Picotti, and
F Massara, and
G M Molinatti, and
P Mantegazza, and
E E Müller
December 1977,
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F Camanni, and
G B Picotti, and
F Massara, and
G M Molinatti, and
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E E Müller
January 1979,
Nihon Naibunpi Gakkai zasshi,
F Camanni, and
G B Picotti, and
F Massara, and
G M Molinatti, and
P Mantegazza, and
E E Müller
August 1975,
Endocrinologia japonica,
F Camanni, and
G B Picotti, and
F Massara, and
G M Molinatti, and
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E E Müller
January 1976,
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F Camanni, and
G B Picotti, and
F Massara, and
G M Molinatti, and
P Mantegazza, and
E E Müller
August 1975,
La Clinica terapeutica,
F Camanni, and
G B Picotti, and
F Massara, and
G M Molinatti, and
P Mantegazza, and
E E Müller
July 1986,
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F Camanni, and
G B Picotti, and
F Massara, and
G M Molinatti, and
P Mantegazza, and
E E Müller
August 1977,
The Journal of clinical endocrinology and metabolism,
F Camanni, and
G B Picotti, and
F Massara, and
G M Molinatti, and
P Mantegazza, and
E E Müller
September 1976,
American journal of obstetrics and gynecology,
F Camanni, and
G B Picotti, and
F Massara, and
G M Molinatti, and
P Mantegazza, and
E E Müller
July 1991,
The International journal of neuroscience,
F Camanni, and
G B Picotti, and
F Massara, and
G M Molinatti, and
P Mantegazza, and
E E Müller
December 1976,
The Journal of clinical endocrinology and metabolism,
