Adrenarche
755393
208036803
2008-04-25T03:55:31Z
75.82.67.247
'''Adrenarche''' refers to a stage of maturation of the cortex of the human [[adrenal gland]]s. It typically occurs between ages 6 and 10 years and involves both structural and functional changes. Adrenarche is a process related to [[puberty]] but distinct from [[hypothalamus|hypothalamic]]-[[pituitary gland|pituitary]]-[[gonad]]al maturation and function.
==Structural and functional changes of adrenarche==
Structural changes of adrenarche include increased size and mass of the adrenal cortex, and completion of differentiation into the three zones: [[zona glomerulosa]], [[zona fasciculata]], and [[zona reticularis]].
One of the primary functional changes is further differentiation of [[sex steroid]] synthesis among the three zones, so that as in adults, the zona glomerlulosa primarily produces [[mineralocorticoid]]s such as [[aldosterone]], the zona fasciculata primarily produces [[glucocorticoid]]s such as [[cortisol]], and the zona reticularis primarily produces [[androgen]]s such as [[dehydroepiandrosterone]], [[dehydroepiandrosterone sulfate]], and [[androstenedione]].
The second important functional change is a steady increase over several years in the daily production of adrenal androgens. A characteristic aspect of early adrenarche is a diminished activity of [[Hydroxysteroid dehydrogenase|3β-hydroxysteroid dehydrogenase]], the [[enzyme]] which mediates the [[hydroxylation]] of [[17-hydroxypregnenolone]] to [[17-hydroxyprogesterone]], and [[dehydroepiandrosterone|DHEA]] to [[androstenedione]]. Blood levels of DHEA, androstenedione, and especially [[dehydroepiandrosterone sulfate|DHEAS]] are useful measures of adrenal maturation.
==Role of adrenarche as part of 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 [[insulin]] 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 [[obesity|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 vulgaris|acne]] may occur. In most boys, these changes are indistinguishable from early [[testis|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 [[ovary|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.
==Premature adrenarche==
'''Premature adrenarche''' is the most common cause of the early appearance of pubic hair ("premature [[pubarche]]") 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 endocrinology|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.
==See also==
* [[adrenal cortex]]
* [[androgen]]s
* [[puberty]]
* [[precocious puberty]]
==External links==
* {{MeshName|Adrenarche}}
{{Reproductive physiology}}
[[Category:Endocrine system]]
[[pl:Adrenarche]]