Increased serum prolactin but normal TSH during prolonged domperidone treatment in children

The influence of the dopamine receptor blocking agent domperidone on prolactin and TSH secretion was studied in 16 infants, aged 10-360 days, who were treated for gastroesophageal reflux. The pretreatment serum prolactin levels were not statistically different from the levels in age-matched controls and showed the well-known inverse relationship with age. During treatment with domperidone a significant increase in prolactin level was observed on days 1, 4 and 21-28, the mean values on these three days not being statistically different. No correlation could be found between the serum prolactin levels and the corresponding plasma domperidone levels. One infant of this series and three not included in this series developed reversible breast hypertrophy with galactorrhoea in three of them: in none of them was the prolactin level, corrected for age, above 1 SD of the mean. All had received relatively high doses of domperidone. In 13 patients domperidone did not influence TSH secretion.