Turner syndromeTurner syndrome (TS), also known as 45,X, or 45,X0, is a genetic disorder in which a female has a single X chromosome, compared to the two sex chromosomes (XX or XY) in most people. Signs and symptoms vary among those affected. Often, a short and webbed neck, low-set ears, low hairline at the back of the neck, short stature, and swollen hands and feet are seen at birth. Typically, those affected do not develop menstrual periods or breasts without hormone treatment and are unable to have children without reproductive technology.
XYY syndromeXYY syndrome, also known as Jacobs syndrome, is an aneuploid genetic condition in which a male has an extra Y chromosome. There are usually few symptoms. These may include being taller than average and an increased risk of learning disabilities. The person is generally otherwise normal, including typical rates of fertility. The condition is generally not inherited but rather occurs as a result of a random event during sperm development. Diagnosis is by a chromosomal analysis, but most of those affected are not diagnosed within their lifetime.
5α-Reductase 2 deficiency5α-Reductase 2 deficiency (5αR2D) is an autosomal recessive condition caused by a mutation in SRD5A2, a gene encoding the enzyme 5α-reductase type 2 (5αR2). The condition is rare, affects only genetic males, and has a broad spectrum. 5αR2 is expressed in specific tissues and catalyzes the transformation of testosterone (T) to 5α-dihydrotestosterone (DHT). DHT plays a key role in the process of sexual differentiation in the external genitalia and prostate during development of the male fetus.
Androgen insensitivity syndromeAndrogen insensitivity syndrome (AIS) is a difference in sex development involving hormonal resistance due to androgen receptor dysfunction. It affects 1 in 20,000 to 64,000 XY (karyotypically male) births. The condition results in the partial or complete inability of cells to respond to androgens. This unresponsiveness can impair or prevent the development of male genitals, as well as impairing or preventing the development of male secondary sexual characteristics at puberty.
HormoneA hormone (from the Greek participle ὁρμῶν, "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required for the correct development of animals, plants and fungi. Due to the broad definition of a hormone (as a signaling molecule that exerts its effects far from its site of production), numerous kinds of molecules can be classified as hormones.
Klinefelter syndromeKlinefelter syndrome (KS), also known as 47,XXY, is an aneuploid genetic condition where a male has an additional copy of the X chromosome. The primary features are infertility and small, poorly functioning testicles. Usually, symptoms are subtle and subjects do not realize they are affected. Sometimes, symptoms are more evident and may include weaker muscles, greater height, poor motor coordination, less body hair, breast growth, and less interest in sex. Often, these symptoms are noticed only at puberty.
5α-Reductase5α-Reductases, also known as 3-oxo-5α-steroid 4-dehydrogenases, are enzymes involved in steroid metabolism. They participate in three metabolic pathways: bile acid biosynthesis, androgen and estrogen metabolism. There are three isozymes of 5α-reductase encoded by the genes SRD5A1, SRD5A2, and SRD5A3. 5α-Reductases catalyze the following generalized chemical reaction: a 3-oxo-5α-steroid + acceptor a 3-oxo-Δ4-steroid + reduced acceptor Where a 3-oxo-5α-steroid and acceptor are substrates, and a corresponding 3-oxo-Δ4-steroid and the reduced acceptor are products.
Growth hormone–releasing hormoneGrowth hormone–releasing hormone (GHRH), also known as somatocrinin or by several other names in its endogenous forms and as somatorelin (INN) in its pharmaceutical form, is a releasing hormone of growth hormone (GH). It is a 44-amino acid peptide hormone produced in the arcuate nucleus of the hypothalamus. GHRH first appears in the human hypothalamus between 18 and 29 weeks of gestation, which corresponds to the start of production of growth hormone and other somatotropes in fetuses.
Releasing and inhibiting hormonesReleasing hormones and inhibiting hormones are hormones whose main purpose is to control the release of other hormones, either by stimulating or inhibiting their release. They are also called liberins (ˈlɪbərᵻnz) and statins (ˈstætᵻnz) (respectively), or releasing factors and inhibiting factors. The principal examples are hypothalamic-pituitary hormones that can be classified from several viewpoints: they are hypothalamic hormones (originating in the hypothalamus), they are hypophysiotropic hormones (affecting the hypophysis, that is, the pituitary gland), and they are tropic hormones (having other endocrine glands as their target).
Growth hormoneGrowth hormone (GH) or somatotropin, also known as human growth hormone (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in human development. GH also stimulates production of IGF-1 and increases the concentration of glucose and free fatty acids. It is a type of mitogen which is specific only to the receptors on certain types of cells.
Genetic disorderA genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders are the most common, the term is mostly used when discussing disorders with a single genetic cause, either in a gene or chromosome. The mutation responsible can occur spontaneously before embryonic development (a de novo mutation), or it can be inherited from two parents who are carriers of a faulty gene (autosomal recessive inheritance) or from a parent with the disorder (autosomal dominant inheritance).
PseudohermaphroditismPseudohermaphroditism is a condition in which an individual has a matching chromosomal and gonadal tissue (ovary or testis) sex, but mismatching external genitalia. Female pseudohermaphroditism refers to an individual with ovaries and external genitalia resembling those of a male. Male pseudohermaphroditism refers to an individual with testes and external genitalia resembling those of a female. In some cases, external sex organs associated with pseudohermaphroditism appear intermediate between a typical clitoris and penis.
PubertyPuberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a boy. In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs. Physical growth—height and weight—accelerates in the first half of puberty and is completed when an adult body has been developed.
Noonan syndromeNoonan syndrome (NS) is a genetic disorder that may present with mildly unusual facial features, short height, congenital heart disease, bleeding problems, and skeletal malformations. Facial features include widely spaced eyes, light-colored eyes, low-set ears, a short neck, and a small lower jaw. Heart problems may include pulmonary valve stenosis. The breast bone may either protrude or be sunken, while the spine may be abnormally curved. Intelligence is often normal. Complications of NS can include leukemia.
Complete androgen insensitivity syndromeComplete androgen insensitivity syndrome (CAIS) is an AIS condition that results in the complete inability of the cell to respond to androgens. As such, the insensitivity to androgens is only clinically significant when it occurs in individuals who are exposed to significant amounts of testosterone at some point in their lives. The unresponsiveness of the cell to the presence of androgenic hormones prevents the masculinization of male genitalia in the developing fetus, as well as the development of male secondary sexual characteristics at puberty, but does allow, without significant impairment, female genital and sexual development in those with the condition.
Genetic counselingGenetic counseling is the process of investigating individuals and families affected by or at risk of genetic disorders to help them understand and adapt to the medical, psychological and familial implications of genetic contributions to disease. This field is considered necessary for the implementation of genomic medicine.
Genetic testingGenetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or through biochemical analysis to measure specific protein output. In a medical setting, genetic testing can be used to diagnose or rule out suspected genetic disorders, predict risks for specific conditions, or gain information that can be used to customize medical treatments based on an individual's genetic makeup.
Estrogen insensitivity syndromeEstrogen insensitivity syndrome (EIS), or estrogen resistance, is a form of congenital estrogen deficiency or hypoestrogenism which is caused by a defective estrogen receptor (ER) – specifically, the estrogen receptor alpha (ERα) – that results in an inability of estrogen to mediate its biological effects in the body. Congenital estrogen deficiency can alternatively be caused by a defect in aromatase, the enzyme responsible for the biosynthesis of estrogens, a condition which is referred to as aromatase deficiency and is similar in symptomatology to EIS.
Sex-determining region Y protein'Sex-determining region Y protein' (SRY), or testis-determining factor (TDF), is a DNA-binding protein (also known as gene-regulatory protein/transcription factor) encoded by the SRY gene that is responsible for the initiation of male sex determination in therian mammals (placental mammals and marsupials). SRY is an intronless sex-determining gene on the Y chromosome. Mutations in this gene lead to a range of disorders of sex development with varying effects on an individual's phenotype and genotype.
HypogonadismHypogonadism means diminished functional activity of the gonads—the testes or the ovaries—that may result in diminished production of sex hormones. Low androgen (e.g., testosterone) levels are referred to as hypoandrogenism and low estrogen (e.g., estradiol) as hypoestrogenism. These are responsible for the observed signs and symptoms in both males and females. Hypogonadism, commonly referred to by the symptom "low testosterone" or "Low T", can also decrease other hormones secreted by the gonads including progesterone, DHEA, anti-Müllerian hormone, activin, and inhibin.
