HYPERPROLACTINEMIA, A TOOL IN TREATMENT CONTROL OF TETRAHYDROBIOPTERIN DEFICIENCY - ENDOCRINE STUDIES IN AN AFFECTED GIRL

Severe tetrahydrobiopterin (BH4) deficiency is a naturally occurring m odel of cerebral catecholamine and serotonin shortage. Examination of the stimulated release and physiologic secretion pattern of several ho rmones in affected individuals permits certain conclusions concerning the involvement of these neurotransmitters in hormone regulation. Trea tment, moreover, permits the ranking of the quality of the therapeutic regimens in use according to the degree of hormonal alteration. The 2 4-h secretion pattern of prolactin, GH, cortisol, and melatonin and th e stimulated release of prolactin, GH, TSH, and gonadotropins were stu died in an affected girl. Severe hyperprolactinemia with disruption of the pulsatile and circadian secretion pattern was the prevailing feat ure. The GH physiologic secretion pattern was not affected, but its st imulation was impaired. Melatonin displayed a normal circadian secreti on pattern; the rhythm, however, was advanced by several hours. Conven tional treatment of BH4 deficiency,i.e. BH4, 5-hydroxytryptophan, and L-DOPA/carbidopa (the last named given in three doses per day), suppre sses prolactin levels merely for a few hours. L-DOPA/carbidopa given a t shorter intervals or, even better, as a slow release preparation, is more effective in suppressing prolactin levels. Our data indicate imm ense hyperprolactinemia but few other hormonal disturbances in severe BH4 deficiency. Prolactin secretion may serve as an extremely sensitiv e marker for the hypothalamic dopamine content under different therape utic regimens. Treatment with an L-DOPA/carbidopa slow release prepara tion produces virtually normal prolactin levels.