Prolactinoma associated with transient growth hormone deficiency but persistent growth retardation

A 14.8 year old boy was evaluated for galactorrhea of two months duration and growth deceleration for greater than three years. He was 3.7 standard deviations (SD) below the mean for age in height and euthyroid with uncompromised vision, bilateral galactorrhea, and pubertal arrest. MRI demonstrated a 10 x 8 mm left pituitary mass. Bone age was 11.5 years. Serum prolactin (PRL) decreased by more than 85% after 5 weeks of treatment with bromocriptine (Br). After five months, the prolactinoma (PRLoma) measured 5 x 4 mm. Hypothalamic-pituitary function indicated growth hormone (GH) deficiency and hypogonadotropic hypogonadism as assessed by ITT-TRH-GnRH-clonidine. After nine months of Br, despite return of adequate gonadotropin and GH secretion as assessed by repeat ITT-TRH-GnRH-clonidine, pooled 12 hour nocturnal spontaneous GH secretion, and clinical progression of puberty, there was no linear "catch-up growth" (growth rate = 4.4 cm/yr and height 4.2 SD below the mean for age). Growth rate increased following supplemental GH administration without untoward effect. We conclude that there may be discordance/lag between reduction in secretion and size of PRLomas and growth despite resolution of other anterior pituitary dysfunction. Other possibilities are discussed.