Delayed puberty as described earlier has a statistical definition based on epidemiological studies. Onset of development, which includes tightly related growth and pubertal development, has a variable timing that depends on genetic and environmental factors. This means that some of the girls who present delayed puberty, generally associated with growth delay and short stature (2SD below mean values for height for age) do not have any illness but present a simple variation in the timing of development. In this case, follow-up shows the spontaneous onset of the development of secondary sex characteristics and the acceleration of growth velocity.

However, it is sometimes difficult in the beginning to differentiate between CDGP and true IHH, although some signs can orient the treatment. Evaluation and follow-up are in any case necessary and the principal goal of the clinical, biological and radiological exams is to eliminate organic disease. There might be similar cases of CDGP in parents or siblings.

First of all, true somatotropic deficiency must be eliminated. In CDGP, short stature and slow growth velocity correlate well with bone age, which reflects delayed puberty and not chronological age. GH secretion may be low on basal levels while stimulation tests are positive, although at a suboptimal level, corresponding in fact to the true prepubertal status. There are no real hormonal deficiencies as evidenced by combined pituitary function tests and systematic radiological examination such as MRI does not show any tumoral image or abnormal infiltration.

Medical history does not reveal known chronic disease. Celiac disease has been eliminated by negative specific antibodies. Functional delayed puberty with a negative energetic balance must also be eliminated by studying nutritional, psychological and athletic background. It is particularly important to screen selective food behavior or disorders suggesting anorexia nervosa or a severely conflicted affective relationship. In fact, the most difficult differential diagnosis is with IHH in the beginning before regular follow-up. However, adrenarche is also delayed in CDGP but not in IHH. Growth is not delayed in IHH and there is no short stature for age.

There are no associated signs such as anosmia, obesity, or malformations in CDGP and when bone age exceeds 11 years, usually pubertal development begins. Biological hormonal data (basal plasma LH, FSH levels, urinary gonadotropins), response to a stimulation test with LHRH, and pulsatile LHRH are statistically lower for IHH than for CDGP and become discriminative for a bone age of 11 years. Lack of LH pulses is highly suggestive for IHH but more difficult to study (measured for 24 h at 10-min intervals). FSH level has been strongly related to lack of LH pulses and LH response to LHRH agonist seems to be more discriminative than the LHRH stimulation test.