Long-Term Growth Hormone Therapy in Adulthood Results in Significant Linear Growth in Siblings with a PROP-1 Gene Mutation

PROP-1 gene mutations result in impaired production of GH, gonadotropins, TSH, and prolactin. We describe three adult siblings, aged 18-25 yr, with short stature, hypothyroidism, and lack of pubertal maturation, who were homozygous for 301-302delAG PROP-1 mutation. We had the unique opportunity to treat them in adulthood with GH for 4-5 yr and thyroid replacement before sex steroid replacement. Sibling 1, a female, had a chronological age (CA) of 25 yr 8 months, a bone age (BA) of 12.5 yr, and height of 128.7 cm [-5.29 sd score (SDS)]; sibling 2, a younger sister had a CA of 22 yr 5 months, a BA of 13 yr, and height of 137.5 cm (-3.94 SDS); and sibling 3, a male, had a CA of 18 yr 4 months, a BA of 11.5 yr, and height of 127.5 cm (-6.38 SDS). Despite delay in treatment and fairly advanced BA, all responded to GH and thyroid hormone therapy with a dramatic increase in linear growth: 22.3 cm for sibling 1, 22 cm for sibling 2, and 34.5 cm for sibling 3. After sex hormone replacement, siblings 1, 2, and 3 grew another 2.6, 3, and 9.5 cm to final heights of 153.6, 162.5, and 171.5 cm, respectively. In conclusion, the substantial linear growth in adult siblings with a PROP-1 mutation illustrates that despite an advanced BA, linear growth potential remains in adulthood in the setting of sex steroid deficiency.