Effect of hgH on head circumference and IQ in isolated growth hormone deficiency

Repeated testing of IQ and head circumference in 4 children with isolated growth hormone deficiency (IGHD) revealed a catch-up in both parameters in 2 patients treated at ages $\text{3}\text{3}\text{12}$ and $\text{4}\text{5}\text{12}$, but in 2 patients treated at ages $\text{9}\text{1}\text{12}$ and $\text{13}\text{5}\text{12}$, no improvement was found.