Adrenarche
Encyclopedia
Adrenarche is an early sexual maturation stage in some higher primate
s that in human
s typically occurs at around 6 to 8 years of age. During adrenarche the adrenal cortex
secretes increased levels of androgen
s such as DHEA and DHEAS, but without increased cortisol
levels. Adrenarche is the result of the development of a new zone of the adrenal cortex, the zona reticularis
. Adrenarche is a process related to puberty
, but distinct from hypothalamic
-pituitary
-gonad
al maturation and function.
s and gorilla
s show a pattern of adrenarche development similar to humans.
and leptin
. Many children born small for gestational age (SGA) because of intrauterine growth retardation (IUGR) have an earlier onset of adrenarche, which raises the possibility that timing of adrenarche may be affected by physiological programming in infancy. Adrenarche also occurs prematurely in many children who are overweight
, suggesting a possible relationship with body mass or adiposity signals.
The principal physical consequences of adrenarche are androgen
effects, especially pubic hair
(in which Tanner stage
2 becomes Tanner stage 3) and the change of sweat
composition that produces adult body odor
. Increased oiliness of the skin and hair and mild acne
may occur. In most boys, these changes are indistinguishable from early testicular testosterone
effects occurring at the beginning of gonadal puberty. In girls, the adrenal androgens of adrenarche produce most of the early androgenic changes of puberty: pubic hair, body odor, skin oiliness, and acne. In most girls the early androgen effects coincide with, or are a few months behind, the earliest estrogen
ic effects of gonadal puberty (breast development and growth acceleration). As female puberty progresses, the ovaries
and peripheral tissues become more important sources of androgens.
Parents and many physicians often infer (incorrectly) the onset of puberty from the first appearance of pubic hair
(termed pubarche
). However, the independence of adrenarche and gonadal puberty is apparent in children with atypical or abnormal development, when one process may occur without the other. For instance, adrenarche does not occur in many girls with Addison's disease
, who will continue to have minimal pubic hair as puberty progresses. Conversely, girls with Turner syndrome
will have normal adrenarche and normal pubic hair development, but true gonadal puberty never occurs because their ovaries are defective.
") in childhood. In a large proportion of children it seems to be a variation of normal development requiring no treatment. However, there are three clinical issues related to premature adrenarche.
First, when pubic hair appears at an unusually early age in a child, premature adrenarche should be distinguished from true central precocious puberty
, from congenital adrenal hyperplasia
, and from androgen-producing tumors of the adrenals or gonads. Pediatric endocrinologists
do this by demonstrating advanced levels of DHEAS and other adrenal androgens, with prepubertal levels of gonadotropin
s and gonadal sex steroid
s.
Second, there is some evidence that premature adrenarche may indicate that there was an abnormality of intrauterine energy environment and growth. As mentioned above, premature adrenarche occurs more often in children with intrauterine growth retardation and in overweight children. Some of these same studes have demonstrated that some girls who display premature adrenarche may continue to have excessive androgen levels in adolescence. This can result in hirsutism
or menstrual irregularities due to anovulation
referred to as polycystic ovary syndrome
.
Third, at least one report found an increased incidence of behavior and school problems in a group of children with premature adrenarche compared with an otherwise similar control group. To date such a relationship has neither been confirmed nor explained and there are no obvious management implications.
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
s that in human
Human
Humans are the only living species in the Homo genus...
s typically occurs at around 6 to 8 years of age. During adrenarche the adrenal cortex
Adrenal cortex
Situated along the perimeter of the adrenal gland, the adrenal cortex mediates the stress response through the production of mineralocorticoids and glucocorticoids, including aldosterone and cortisol respectively. It is also a secondary site of androgen synthesis.-Layers:Notably, the reticularis in...
secretes increased levels of androgen
Androgen
Androgen, also called androgenic hormone or testoid, is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors...
s such as DHEA and DHEAS, but without increased cortisol
Cortisol
Cortisol is a steroid hormone, more specifically a glucocorticoid, produced by the adrenal gland. It is released in response to stress and a low level of blood glucocorticoids. Its primary functions are to increase blood sugar through gluconeogenesis; suppress the immune system; and aid in fat,...
levels. Adrenarche is the result of the development of a new zone of the adrenal cortex, the zona reticularis
Zona reticularis
The zona reticularis is the innermost layer of the adrenal cortex, lying deep to the zona fasciculata and superficial to the adrenal medulla. The cells are arranged cords that project in different directions giving a net-like appearance The zona reticularis is the innermost layer of the adrenal...
. Adrenarche is a process related to puberty
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
, but distinct from hypothalamic
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
-pituitary
Pituitary gland
In vertebrate anatomy the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 g , in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity covered by a dural fold...
-gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
al maturation and function.
Animal prevalence
Adrenarche occurs in only a small number of primates, and only chimpanzeeChimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
s and gorilla
Gorilla
Gorillas are the largest extant species of primates. They are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Africa. Gorillas are divided into two species and either four or five subspecies...
s show a pattern of adrenarche development similar to humans.
Role in puberty
An initiator of adrenarche has not yet been identified. Researchers have unsuccessfully tried to identify a new pituitary peptide, to be called "adrenal androgen stimulating hormone". Others have proposed that adrenarchal maturation is a gradual process intrinsic to the adrenal glands that has no distinct trigger. A third avenue of research is pursuing a possible relationship with either fetal or childhood body mass and related signals such as insulinInsulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
and leptin
Leptin
Leptin is a 16 kDa protein hormone that plays a key role in regulating energy intake and energy expenditure, including appetite and metabolism. It is one of the most important adipose derived hormones...
. Many children born small for gestational age (SGA) because of intrauterine growth retardation (IUGR) have an earlier onset of adrenarche, which raises the possibility that timing of adrenarche may be affected by physiological programming in infancy. Adrenarche also occurs prematurely in many children who are overweight
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
, suggesting a possible relationship with body mass or adiposity signals.
The principal physical consequences of adrenarche are androgen
Androgen
Androgen, also called androgenic hormone or testoid, is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors...
effects, especially pubic hair
Pubic hair
Pubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region....
(in which Tanner stage
Tanner stage
The Tanner scale is a scale of physical development in children, adolescents and adults. The scale defines physical measurements of development based on external primary and secondary sex characteristics, such as the size of the breasts, genitalia, and development of pubic hair, and was first...
2 becomes Tanner stage 3) and the change of sweat
SWEAT
SWEAT is an OLN/TSN show hosted by Julie Zwillich that aired in 2003-2004.Each of the 13 half-hour episodes of SWEAT features a different outdoor sport: kayaking, mountain biking, ice hockey, beach volleyball, soccer, windsurfing, rowing, Ultimate, triathlon, wakeboarding, snowboarding, telemark...
composition that produces adult body odor
Body odor
Body odor or body odour, sometimes colloquially abbreviated as B.O., is the smell of bacteria growing on the body. The bacteria multiply rapidly in the presence of sweat, but sweat itself is almost completely odorless to humans....
. Increased oiliness of the skin and hair and mild acne
Acne vulgaris
Acne vulgaris is a common human skin disease, characterized by areas of skin with seborrhea , comedones , papules , pustules , Nodules and possibly scarring...
may occur. In most boys, these changes are indistinguishable from early testicular testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...
effects occurring at the beginning of gonadal puberty. In girls, the adrenal androgens of adrenarche produce most of the early androgenic changes of puberty: pubic hair, body odor, skin oiliness, and acne. In most girls the early androgen effects coincide with, or are a few months behind, the earliest estrogen
Estrogen
Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...
ic effects of gonadal puberty (breast development and growth acceleration). As female puberty progresses, the ovaries
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
and peripheral tissues become more important sources of androgens.
Parents and many physicians often infer (incorrectly) the onset of puberty from the first appearance of pubic hair
Pubic hair
Pubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region....
(termed pubarche
Pubarche
Pubarche refers to the first appearance of pubic hair in a child. Pubarche is one of the physical changes of puberty but should not be equated with it since it may occur independently of complete puberty...
). However, the independence of adrenarche and gonadal puberty is apparent in children with atypical or abnormal development, when one process may occur without the other. For instance, adrenarche does not occur in many girls with Addison's disease
Addison's disease
Addison’s disease is a rare, chronic endocrine disorder in which the adrenal glands do not produce sufficient steroid hormones...
, who will continue to have minimal pubic hair as puberty progresses. Conversely, girls with Turner syndrome
Turner syndrome
Turner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent...
will have normal adrenarche and normal pubic hair development, but true gonadal puberty never occurs because their ovaries are defective.
Premature
Premature adrenarche is the most common cause of the early appearance of pubic hair ("premature pubarchePubarche
Pubarche refers to the first appearance of pubic hair in a child. Pubarche is one of the physical changes of puberty but should not be equated with it since it may occur independently of complete puberty...
") in childhood. In a large proportion of children it seems to be a variation of normal development requiring no treatment. However, there are three clinical issues related to premature adrenarche.
First, when pubic hair appears at an unusually early age in a child, premature adrenarche should be distinguished from true central precocious puberty
Precocious puberty
As a medical term, precocious puberty describes puberty occurring at an unusually early age. In most of these children, the process is normal in every respect except the unusually early age, and simply represents a variation of normal development. In a minority of children, the early development is...
, from congenital adrenal hyperplasia
Congenital adrenal hyperplasia
Congenital adrenal hyperplasia refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands ....
, and from androgen-producing tumors of the adrenals or gonads. Pediatric endocrinologists
Pediatric endocrinology
Pediatric endocrinology is a medical subspecialty dealing with variations of physical growth and sexual development in childhood, as well as diabetes and other disorders of the endocrine glands....
do this by demonstrating advanced levels of DHEAS and other adrenal androgens, with prepubertal levels of gonadotropin
Gonadotropin
Gonadotropins are protein hormones secreted by gonadotrope cells of the pituitary gland of vertebrates. This is a family of proteins, which include the mammalian hormones follitropin , lutropin , placental chorionic gonadotropins hCG and eCG and chorionic gonadotropin , as well as at least two...
s and gonadal sex steroid
Sex steroid
Sex steroids, also known as gonadal steroids, are steroid hormones that interact with vertebrate androgen or estrogen receptors. Their effects are mediated by slow genomic mechanisms through nuclear receptors as well as by fast nongenomic mechanisms through membrane-associated receptors and...
s.
Second, there is some evidence that premature adrenarche may indicate that there was an abnormality of intrauterine energy environment and growth. As mentioned above, premature adrenarche occurs more often in children with intrauterine growth retardation and in overweight children. Some of these same studes have demonstrated that some girls who display premature adrenarche may continue to have excessive androgen levels in adolescence. This can result in hirsutism
Hirsutism
Hirsutism or frazonism is the excessive hairiness on women in those parts of the body where terminal hair does not normally occur or is minimal - for example, a beard or chest hair. It refers to a male pattern of body hair and it is therefore primarily of cosmetic and psychological concern...
or menstrual irregularities due to anovulation
Anovulation
An anovulatory cycle is a menstrual cycle during which the ovaries do not release an oocyte. Therefore, ovulation does not take place. However, a woman who does not ovulate at each menstrual cycle is not necessarily going through menopause...
referred to as polycystic ovary syndrome
Polycystic ovary syndrome
Polycystic ovary syndrome is one of the most common female endocrine disorders. PCOS is a complex, heterogeneous disorder of uncertain aetiology, but there is strong evidence that it can to a large degree be classified as a genetic disease....
.
Third, at least one report found an increased incidence of behavior and school problems in a group of children with premature adrenarche compared with an otherwise similar control group. To date such a relationship has neither been confirmed nor explained and there are no obvious management implications.