Consultant Radiologist in Tehran University of Medical Science (TUMS), Arash Hospital, Headmaster of Radiology Department
Precocious puberty is defined as the development of secondary sexual characteristics before the age of 8 years in girls and less than 9 years in boys.
Precocious puberty is caused by a heterogeneous group of disorders, which ranges from idiopathic to malignant tumors.
It is divided into central (gonadotrophin-dependent) precocious puberty and peripheral (gonadotrophin- independent) precocious puberty.
In order to understand the two types of precocious puberty, basic knowledge of normal puberty pertaining to the hypothalamus-pituitary-gonadal (HPG) axis is necessary.
There are several causes of premature sexual development which can be divided into:
a) premature activation of the hypothalamic pituitary-gonadal (HPG) axis (central PP).
b) abnormal patterns of gonadotrophin secretion (premature thelarche, thelarche variant).
c) excess adrenal androgens (adrenarche, congenital adrenal hyperplasia (CAH), adrenal tumours).
d) gonadotrophin independent PP (secretion of sex steroids is independent of the HPG axis).
MRI of the brain, ultrasound of the pelvis/testes or CT of the abdomen are main modality which performed in these group of patient.
According to literature, brain MRI can show spectrum from normal to brain tumor, hydrocephalus ,inflammatory changes and etc.
Abdominal CT scan can be normal or show adrenal hyperplasia or adrenocortical carcinoma.
Although the most valuable parameter for differentiating girls with CPP is the measurement of luteinizing hormone (either the baseline value or after stimulation with gonadotropin-releasing hormone (GnRH) or GnRH analogs), it has been reported in a recent consensus statement that pelvic ultrasound imaging is considered helpful as an adjunct to GnRH stimulation in differentiating CPP from premature thelarche.This consensus statement reported cut-off valuesfor uterine length ranging from 3.4 to 4.0 cm, and between 1.0 and 3.0 cm
For ovarian volume which are going to be discussed in more detail in this lecture.