[Primary amenorrhoea and macrocephaly]

Primary amenorrhoea has a broad differential diagnosis. When hypogonadotropic hypogonadism is present, possible intracranial abnormalities should always be suspected.

We present the case of a 16-year-old girl with primary amenorrhoea. Laboratory investigations showed hypogonadotropic hypogonadism. MRI of the brain revealed a secondary hydrocephalus, caused by a retrocerebellar arachnoid cyst. The increased pressure from the third ventricle on the hypothalamus caused a functional gonadotropin-releasing hormone (GnRH) deficiency, leading to primary amenorrhoea. Menarche occurred after neurosurgical intervention and the patient developed a regular cycle. In hindsight, the hydrocephalus could have been discovered earlier, because of the development of macrocephaly during the first years of life.

This case illustrates the importance of head circumference measurements, even after the first year of life, and the importance of further investigation if an abnormal growth pattern is revealed. Imaging investigations of the brain should always be carried out in cases of primary amenorrhoea accompanied by low gonadotropin levels (central hypogonadism).