12 mg is the largest they make.
From the Genotropin site
---------------------DOSAGE FORMS AND STRENGTHS----------------------
GENOTROPIN lyophilized powder in a two-chamber color-coded cartridge (3):
5 mg (green tip) and 12 mg (purple tip) (with preservative)
GENOTROPIN MINIQUICK Growth Hormone Delivery Device containing a two- chamber cartridge (without preservative):
0.2 mg, 0.4 mg, 0.6 mg, 0.8 mg, 1.0 mg, 1.2 mg, 1.4 mg, 1.6 mg, 1.8 mg, and 2.0 mg