The absence of bearded axillary and pubic hair is seen in Klinefelter syndrome. It is also known as congenital testicular hypoplasia or Klinefelter’s syndrome. The typical karyotype is 47, XXY, and the phenotype is characterized by testicular hypoplasia. The body is elongated, due to an increase in the distance between the heel and the toe bones. In men, the mammary glands are developed, pubic hair is distributed in a feminine pattern, and the penis and testes are small. Severe cases are associated with mental retardation, cryptorchidism and hypospadias. Sometimes it can occur due to some organic diseases, such as hypopituitarism, hypothyroidism, testicular feminization syndrome, etc. Tests for congenital testicular hypoplasia resulting in absence of bearded axillary and pubic hair: 1. Serum testosterone (testosterone,T) measurement: Most cases are reduced. According to statistics, 79% of patients with type 47,XXY had a decrease, 33% of patients with type 46,XY/47,XXY had a decrease, and almost all of patients with type 48,XXXY, 49,XXXYY and 49,XXXXY had a decrease. The decrease was generally mild and severe decrease was rare. 2, Serum follicle stimulating hormone (FSH) and luteinizing hormone (LH) measurements: serum: FSH levels were all increased, without overlap with normal subjects. Serum LH levels were increased in 75% of patients with type 47,XXY; 33% of patients with type 46,XY/47,XXY; and in the majority of patients with type 48,XXXY, 49,XXXYY and 49,XXXXY. 3. Serum estradiol (E2) measurement: increased in most cases, more markedly in patients with gynecomastia. 4.Serum androgen binding protein (ABP) measurement: Most of them have different degrees of increase. 5. Human chorionic gonadotropin (HCG) test: The response of serum T to HCG stimulation is reduced or normal. Most of them are reduced to varying degrees. 6.Gonadotropin-releasing hormone (GnRH) test: The response of serum LH and FSH to GnRH stimulation is often overreactive. 7, sex chromatin examination: oral mucosa scraping examination, where there are 2 or more X chromosomes chromatin (Barr vesicles) is positive. 8, semen examination: most cases are spermless or less sperm, but a few patients with 46, XY/47, XXY type semen examination can be basically normal. 9, chromosome examination: generally take peripheral blood lymphocytes for karyotype typing. Leydig cell hyperplasia, which may be pseudoadenoma-like or nodular hyperplasia.