Browsing Pathways

3-beta-hydroxysteroid dehydrogenase (HSD) deficiency is an extremely rare inborn error of metabolism (IEM) and autosomal recessive disorder of the steroidogenesis pathway. It is caused by an defect in the HSD3B2 gene which encodes for the 3 beta-hydroxysteroid dehydrogenase enzyme, which is responsible for forming cortisol from 11b,17a,21-trihydroxypregnenolone. When the enzyme is not correctly produced, cortisol levels in the cell are lowered, and as cortisol is used in the production of other steroids, it may affect their levels as well. 3-beta-HSD deficiency is characterized by low levels of cortisol produced in the adrenal glands. Symptoms include abnormal genitalia for both males and females, as well as infertility. There is also a more severe salt-wasting form of this deficiency, characterized by dehydration. Treatment for 3-beta-HSD deficiency includes steroid replacement, as well as sex hormone replacement during puberty to allow proper development. Surgery can also be used to correct any genital abnormalities that may occur. It is estimated that 3-beta-HSD deficiency affects less than 1 in 1,000,000 individuals, with around 60 cases reported.

Sterol 27-hydroxylase is a mitochondrial cytochrome P-450 species (CYP27) that catalyzes the first step in the degradation of steroid side chain in cholesterol to produce bile acids in the liver. When there are low concentrations of 27-Hydroxylase, patients will exhibit cerebrotendinous xanthomatosis, an autosomal recessive disorder characterized by the accumulation of cholestanol and cholesterol due to the inability to break down the lipids. The formation of xanthomas (deposits of lipids) in the nervous system and tendons will cause symptoms such as dementia, ataxia, and cataracts. Other symptoms may include damaged liver cells and body tissues.

Congenital adrenal hyperplasia (CAH) refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the steps of biosynthesis of cortisol from cholesterol in the adrenal glands, also known as steroidogenesis. 21-hydroxylase deficiency, also known as CYP21 deficiency or CAH1, is an autosomal recessive disorder that accounts for the vast majority of cases of CAH. This deficiency affects cells in the adrenal cortex of the adrenal glands, and due to the deficiency in an enzyme used in many pathways. This prevents the completion of several hormone biosynthesis pathways, including those producing aldosterone and cortisol, and leads to a buildup of their precursors, including 17a-hydroxypregnenolone, which are then processed by the pathways that produce androgen hormones including testosterone. This disorder can vary in severity, depending on the amount of functional enzyme present. The most severe form is known as the salt-wasting form of 21-hydroxylase, and is caused by a complete lack of functional enzyme. This form is called the salt-wasting form, as the lack of aldosterone produced leads to high levels of sodium excreted in the urine, causing infant blood volume to decrease. High potassium levels in blood are also often observed, but if properly diagnosed, saline solution and hydrocortisone can restore normal blood levels and sodium content. In addition, males are typically visually unaffected, but females often possess ambiguous genitalia due to the excess exposure to testosterone during development. The second most severe form is known as the simple virilising form, which does not involve the salt loss of the salt-wasting form, due to a partially functional 21-hydroxylase enzyme. However, the androgen hormones build up similarly, leading to females with some amount of virilisation, or some amount of male characteristics, including ambiguous genitalia. The third and least severe form, known as the non-classical or late onset form, has the highest function in 21-hydroxylase enzymes, and leads to the smallest buildup of androgen hormones. This means that females exhibit little to no virilisation at birth, but as they age can experience male-associated hair growth and baldness, as well as decreased fertility and menstruation irregularities. It can also lead to an early puberty in both males and females, though treatment can help prevent this if it is caught in time.

2-Methyl-3-hydroxybutyryl CoA dehydrogenase deficiency (Hydroxyl-CoA dehydrogenase deficiency; MHBD) is a rare inborn disease of metabolism caused by a mutation in the HSD17B10 gene which codes for 3-hydroxyacyl-CoA dehydrogenase type-2. A deficiency in this enzyme results in accumulation of L-lactic acid in blood, spinal fluid, and urine; 2-ethylhydracrylic acid, 2-methyl-3-hydroxybutyric acid, and tiglylglycine in urine. Symptoms include cerebal atrophy, motor and mental retardation, overactivity and behavior issues, seizures and progressive neurological defects leading to early death. Treatment includes a high carbohydrate and low protein diet.

2-Methyl-3-hydroxybutyryl CoA dehydrogenase deficiency (Hydroxyl-CoA dehydrogenase deficiency; MHBD) is a rare inborn disease of metabolism caused by a mutation in the HSD17B10 gene which codes for 3-hydroxyacyl-CoA dehydrogenase type-2. A deficiency in this enzyme results in accumulation of L-lactic acid in blood, spinal fluid, and urine; 2-ethylhydracrylic acid, 2-methyl-3-hydroxybutyric acid, and tiglylglycine in urine. Symptoms include cerebal atrophy, motor and mental retardation, overactivity and behavior issues, seizures and progressive neurological defects leading to early death. Treatment includes a high carbohydrate and low protein diet.

2-mercaptobenzothiazole is a drug that is not metabolized by the human body as determined by current research and biotransformer analysis. 2-mercaptobenzothiazole passes through the liver and is then excreted from the body mainly through the kidney.

2-Ketoglutarate dehydrogenase complex deficiency, also known as alpha-ketoglutarate dehydrogenase deficiency or oxoglutaric aciduria, is an autosomal recessive disorder of the Krebs cycle caused by a defective oxoglutarate dehydrogenase complex (OGDC). OGDC catalyzes the conversion of 2-ketoglutarate into succinyl-CoA. This disorder is characterized by a large accumulation of 2-ketoglutarate in the urine. Symptoms of the disorder include opisthotonus, ataxia, developmental delay, and seizures.

2-Ketoglutarate dehydrogenase complex deficiency, also known as alpha-ketoglutarate dehydrogenase deficiency or oxoglutaric aciduria, is an autosomal recessive disorder of the Krebs cycle caused by a defective oxoglutarate dehydrogenase complex (OGDC). OGDC catalyzes the conversion of 2-ketoglutarate into succinyl-CoA. This disorder is characterized by a large accumulation of 2-ketoglutarate in the urine. Symptoms of the disorder include opisthotonus, ataxia, developmental delay, and seizures.

L-2-Hydroxyglutaric Aciduria (D-2-Hydroxyglutaric Aciduria ) is an autosomal recessive disease caused by a mutation in the L2HGDH gene which codes for L-2-Hydroxygluarate dehydrogenase. A deficiency in this enzyme results in accumulation of L-2-Hydroxyglutaric acid in plasma, spinal fluid, and urine; and L-lysine in plasma and spinal fluid. Symptoms, which present at birth, include ataxia, hypotonia, mental retardation, and seizures. Premature death often results. D-2-Hydroxyglutaric Aciduria is an autosomal recessive disease caused by a mutation in the D2HGDH gene which does for D-2-Hydroxygluarate dehydrogenase. A deficiency in this enzyme results in accumulation of D-2-Hydroxyglutaric acid in plasma, spinal fluid, and urine; oxoglutaric acid in urine; and gabba-aminobutyric acid in spinal fluid. Symptoms, which present at birth, include ataxia, hypotonia, mental retardation, and seizures. Premature death often results.