Summary
To ascertain the frequency of subcutaneous IGF-1 administration necessary to promote
growth we examined the weight gain of male homozygous lit/lit mice in response to
either sc. IGF-1 or bovine GH administration. Lit/lit mice showed a dose dependent
response to treatment with GH. Bovine GH induced a response in body weight gain within
3 days of the start of treatment. Following a single subcutaneous injection of IGF-1,
plasma IGF-1 levels were elevated for 4-6 hours. Three treatment schedules for IGF-1
were used (once daily, twice daily and four times daily), each employing the same
total daily dose of IGF-1 (30 ug). With IGF-1 treatment, a significant effect on body
weight gain was obtained when administered four times daily. The growth rate with
IGF-1 treatment 6 hourly was similar to that observed following treatment with bGH
(10 ug sc daily). Twelve hourly IGF-1 administration only had a significant effect
on body weight gain when weight was measured in the evening. Lit/lit mice treated
once daily with 30 ug IGF-1 had no weight gain response and became severely hypoglycaemic.
Frequent subcutaneous IGF-1 administration is one approach to growth enhancement in
GH deficiency; higher doses administered less frequently do not promote growth and
may cause hypoglycaemia.
Key words
Insulin-Like Growth Factor 1 - Bovine Growth Hormone - Growth Rate - Hypoglycaemia
