Objective-To study the lactational and hormonal responses to nasal administration of thyrotrophin-releasing hormonc (TRH) in puerperal women with inadequate lactation. Design-Prospective randomized double-blind placebo-controlled study. Subjects-19 pucrperal womcn with inadequate lactation (<50% of normal milk yield) on the 5th day postpartum. Interventions-10 women were allocated to receive TRH administered by a nasal spray of 1 mg, four times daily, between suckling episodes, for 10 consecutive days starting on day 6 postpartum. Nine women werc allocated to receive placebo sprays. Main outcome measures-Daily milk yield, serum lcvcls of prolactin and thyroid hormoncs. Results-Before trcatment all the women had significant prolactin responses to TRH and suckling stimuli. At the end of 10 days of treatment, milk yield incrcascd significantly in the TRH group from a mean of 1424 (SD 33.9) to 2534 (SD 105.3) @day (P = 0414). There was no significant change in the placebo group. Basal prolactin levels increased from a mean of 117.4 pgA (SD 45.2) to 173.3 pg/l (SD 55.5) (P