Congenital causes of central hypogonadism (low Testosterone, low or inappropiately normal LH)
| Isolated hypogonadotropic hypogonadism (IHH) | |
| Anosmic form of IHH (Kallmann syndrome [KS]) | Mutated Gene |
| ANOS1 formerly KAL1 (X-linked recessive) | |
| SEMA3A (Autosomal Dominant) | |
| SOX10 (Autosomal Dominant) | |
| IL17RD (Autosomal Dominant) | |
| FEZF1 (Autosomal Recessive) | |
| Normosmic form of IHH | Mutated Gene |
| KISS1R (Autosomal Recessive) | |
| KISS1 (Autosomal Recessive) | |
| GNRHR (Autosomal Recessive) | |
| GNRH1 (Autosomal Recessive) | |
| TAC3 and TAC3R (Autosomal Recessive) | |
| Anosmic and Normosmic forms of IHH | Mutated Gene |
| PROK2 and PROKR2 (Autosomal Recessive) | |
| FGF8 (Autosomal Dominant) | |
| FGFR1 (Autosomal Dominant) | |
| CHD7 (Autosomal Dominant) | |
| HS6ST1 (Oligogenic Inheritance together with FGFR1 and NSMF) | |
| FGF17 (Oligogenic Inheritance together with IL17RD, DUSP6, SPRY4, and FLRT3) | |
| NSMF (Oligogenic Inheritance together with FGFR1 and HS6ST1) | |
| DUSP6 (Oligogenic inheritance) | |
| SPRY4 (Oligogenic inheritance with DUSP6 and FGFR1) | |
| RFLT3 (Oligogenic inheritance with FGF17, HS6ST1, and FGFR1) | |
| WDR11(Oligogenic inheritance) | |
| AXL (Oligogenic inheritance) | |
| Digenic Anosmic forms of IHH | Mutated genes |
| Heterozygous mutation FGFR1 and Heterozygous deletion NSMF | |
| Digenic Normosmic forms of IHH | Mutated genes |
| Compound heterozygous mutation of GNRHR and heterozygous mutation FGFR1 | |
| IHH associated with obesity | Mutated genes |
| Leptin or leptin receptor mutations | LEP, LEPR |
| IHH associated with Mental Retardation | Genetic Abnormality |
| Prader Willi Syndrome (PWS) | Loss of paternal copy of the PWS "critical region” on chromosome 15q11.2-13 |
| IHH associated with ß-subunit mutations | Genetic Abnormality |
| ß-subunit of LH | |
| ß-subunit of FSH | |
| Deficiencies of multiple pituitary hormones | Pituitary gland differentiation genes |
| LHX3, LHX4, HESX1, and PROP-1 | |
| Acquired causes of secondary hypogonadism | |
| Suppression of gonadotropins release | Conditions leading to suppression of gonadotropin release |
| Hyperprolactinemia | |
| Exogenous sex steroids | |
| Opioid induced hypogonadism | |
| Therapeutic use of GnRH agonists | |
| Acute critical illness | |
| Chronic illness (COPD, CHF, cirrhosis, AIDS, ESRD) | |
| T2DM | |
| Obesity | |
| Anorexia nervosa | |
| Chronic glucocorticoid treatment | |
| Damage to gonadotrophs | Conditions leading to damage of gonadotrophs |
| Pituitary adenoma/cyst/carcinoma | |
| Infiltrative diseases: Langerhans cell histiocytosis, hemochromatosis, sarcoidosis | |
| Infectious: meningitis, tubercolosis | |
| Pituitary apoplexy | |
| Head trauma, traumatic brain injury | |
| Idiopathic | |