CATCH-UP GROWTH INDUCED BY GROWTH-HORMONE IN THE CRANIOFACIAL SKELETON OF THE SNELL STRAIN OF THE HYPOPITUITARY DWARF MOUSE

Immature Snell strain dwarf mice were treated with human growth hormon e for 20 and 40 days, between the ages of 22 and 41 days and 22 and 61 days, respectively. Mature dwarfs were similarly treated for 20 and 4 0 days between the ages of 62 and 81 days and 62 and 101 days, respect ively. These groups of treated mice were compared with untreated dwarf s and normal mice reared under the same conditions. The catch-up growt h effected by human growth hormone on the craniofacial and somatic dev elopment of the Snell strain dwarf mouse at both immature and mature a ges was considerable, overall being approximately 14 per cent. Neurocr anial parameters tended toward the values of normal mice achieving 89- 98 per cent of normal growth. Viscerocranial parameters showed greater catch-up, from a lower start point, reaching 81-93 per cent of the co ntrol. This catch-up growth in mature mice (aged 82-102 days) was at a time when any substantial growth in either dwarf or normal mice has u sually ceased.