[2][3] Babies diagnosed with type IA are shorter than average at birth, which is a clear sign of growth failure.

People with type IB typically exhibit growth failure in their early to mid-childhood years.

[4] Similar to type II isolated growth hormone deficiency, type III is characterized by extremely low growth hormone levels and variable degrees of short height in the affected individuals.

[4] While the majority of isolated growth hormone deficiency cases are sporadic and assumed to be caused by hypothalamic or pituitary injuries in utero, during or after birth, anatomic abnormalities are discovered in just 12% of such patients who undergo magnetic resonance imaging (MRI).

Rarely, heterozygous mutations in SOX3 or HESX13 might cause an isolated growth hormone deficit.