Instruct: Given a question, retrieve relevant documents that answer the question.
Query: Where is the adrenal gland located in the human body?
The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol.[1][2] They are found above the kidneys. Each gland has an outer cortex which produces steroid hormones and an inner medulla. The adrenal cortex itself is divided into three zones: the zona glomerulosa, the zona fasciculata and the zona reticularis.[3]
Treatment for Cushing’s syndrome aims to reduce the high levels of cortisol circulating through the human body. The course of action ultimately depends on the cause of the hypersecretion. Cushing’s can be induced by repeated synthetic steroid use to treat inflammatory diseases, or it can also be caused by a tumor in the pituitary gland or adrenal gland. In either case, treatment may rely on removal of the tumor or of the adrenal glands. Without the adrenal glands, the human body is unable to supply the hormones it produces and therefore requires hormone replacement therapy.
The Body Type program asserts that there are four major glands in the human body (pituitary, thyroid, adrenal, and gonadal) and that each individual has one "dominant gland." Ann Louise Gittleman stated that Abravanel developed these ideas as an expansion of speculations by Henry G. Bieler and noted that this was done, "Without directly monitoring the behavior of any gland..." According to Abravanel, men can be P-types, T-types, or A-types, based on the dominant gland, and women can be P-types, T-types, A-types or G-types (only women can be G-types due to the purported overall influence that a woman's sexual glands can have on her body). An individual's dominant gland is claimed to influence his or her body shape, and the glandular secretions that purportedly influence personality, sleeping schedule, metabolic activity, and other characteristics. Certain foods and exercises are claimed promote or inhibit activity among one or more glands, and Abravanel asserts that, people tend to feed their dominant gland first and foremost.
The adrenal glands are located above the kidneys in humans and in front of the kidneys in other animals. The adrenal glands produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. It controls the behaviour during crisis and emotional situations. It stimulates the heart and its conducting tissues and metabolic processes.
The fetal adrenal cortex can be identified within four weeks of gestation. The adrenal cortex originates from the thickening of the intermediate mesoderm.
At five to six weeks of gestation, the mesonephros differentiates into a tissue known as the gonadal ridge. The gonadal ridge produces the steroidogenic cells for both the gonads and the adrenal cortex. The adrenal medulla is derived from ectodermal cells. Cells that will become adrenal tissue move retroperitoneally to the upper portion of the mesonephros. At seven weeks of gestation, the adrenal cells are joined by sympathetic cells that originate from the neural crest to form the adrenal medulla. At the end of the eighth week, the adrenal glands have been encapsulated and have formed a distinct organ above the developing kidneys. At birth, the adrenal glands weight approximately eight to nine grams (twice that of the adult adrenal glands) and are 0.5% of the total body weight. At 25 weeks, the adult adrenal cortex zone develops and is responsible for the primary synthesis of steroids during the early postnatal weeks.
The adrenal glands in a newborn baby are much larger as a proportion of the body size than in an adult.[38] For example, at age three months the glands are four times the size of the kidneys. The size of the glands decreases relatively after birth, mainly because of shrinkage of the cortex. The cortex, which almost completely disappears by age 1, develops again from age 4–5. The glands weigh about 1 g at birth[12] and develop to an adult weight of about 4 grams each.[28] In a fetus the glands are first detectable after the sixth week of development.[12]
The 2 adrenal glands are located on the top of the kidney and have two distinct sections. The outer region called the outer part which is called the adrenal cortex. The adrenal cortex produce the hormones that are essential for life such as Cortisol and Aldosterone. The inner section, or the Adrenal medulla produce hormones that are not essential for life itself but assist the body in its functions, and these would include a hormone such as Adrenaline.
The adrenal medulla () is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the innermost part of the adrenal gland, consisting of cells that secrete epinephrine (adrenaline), norepinephrine (noradrenaline), and a small amount of dopamine in response to stimulation by sympathetic preganglionic neurons.
The hypothalamic–pituitary–adrenal axis (HPA axis or HTPA axis) is a complex set of direct influences and feedback interactions among three components: the hypothalamus, the pituitary gland (a pea-shaped structure located below the thalamus), and the adrenal (also called "suprarenal") glands (small, conical organs on top of the kidneys).
Absent adrenal gland is a rare condition where the adrenal gland is absent at birth. It should not be confused with adrenal insufficiency or congenital adrenal hyperplasia, where the gland is present but may not be functioning adequately.
The adrenal medulla is at the centre of each adrenal gland, and is surrounded by the adrenal cortex. The chromaffin cells of the medulla are the body's main source of the catecholamines adrenaline and noradrenaline, released by the medulla. Approximately 20% noradrenaline (norepinephrine) and 80% adrenaline (epinephrine) are secreted here.[19]
The adrenal glands may not develop at all, or may be fused in the midline behind the aorta.[12] These are associated with other congenital abnormalities, such as failure of the kidneys to develop, or fused kidneys.[12] The gland may develop with a partial or complete absence of the cortex, or may develop in an unusual location.[12]
The adrenal gland produces hormones that affects growth, development and stress, and also helps to regulate kidney function. There are two parts of the adrenal glands, the adrenal cortex and the adrenal medulla. The adrenal cortex produces mineralocorticoids, which regulate salt and water balance within the body, glucocorticoids (including cortisol) which have a wide number of roles within the body, and androgens, hormones with testosterone-like function. The adrenal medulla produces epinephrine (adrenaline) and norepinephrine (noradrenaline). Disorders of the adrenal gland may affect the production of one or more of these hormones.
A comprehensive study of the genomes and transcriptomes of HEK 293 and five derivative cell lines compared the HEK 293 transcriptome with that of human kidney, adrenal, pituitary and central nervous tissue. The HEK 293 pattern most closely resembled that of adrenal cells, which have many neuronal properties. Given the location of the adrenal gland (adrenal means "next to the kidney"), a few adrenal cells could plausibly have appeared in an embryonic kidney derived culture, and could be preferentially transformed by adenovirus. Adenoviruses transform neuronal lineage cells much more efficiently than typical human kidney epithelial cells. An embryonic adrenal precursor cell therefore seems the most likely origin cell of the HEK 293 line. As a consequence, HEK 293 cells should not be used as an "in vitro" model of typical kidney cells.
Non-tropic hormones are hormones that directly stimulate target cells to induce effects. This differs from the tropic hormones, which act on another endocrine gland.
Non-tropic hormones are those that act directly on targeted tissues or cells, and not on other endocrine gland to stimulate release of other hormones. Many hormones act in a chain reaction. Tropic hormones usually act in the beginning of the reaction stimulating other endocrine gland to eventually release non-tropic hormones. These are the ones that act in the end of the chain reaction on other cells that are not part of other endocrine gland. 
The Hypothalamic-pituitary-adrenal axis is a perfect example of this chain reaction. The reaction begins in the hypothalamus with a release of corticotropin-releasing hormone/factor (CRH/F; tropic). This stimulates the anterior pituitary and causes it to release Adrenocorticotropic hormone (ACTH; tropic) to the adrenal glands. Lastly, cortisol (non-tropic) is secreted from the adrenal glands and goes into the bloodstream where it can have more widespread effects on organs and tissues. Since cortisol is what finally reaches other tissues in the body, it is a non-tropic hormone. CRH an ACTH are tropic hormones because they act on the anterior pituitary gland and adrenal glands, respectively, both of which are endocrine glands. 
Non-tropic hormones are thus often the last piece of a larger process and chain of hormone secretion. Both tropic and non-tropic hormones are necessary for proper endocrine function. For example, if ACTH (Adrenocorticotropin hormone; a tropic hormone) is inhibited, cortisol can no longer be released because the chain reaction has been interrupted. 
Some examples of non-tropic hormones are: 
Most endocrine glands, such as the gonads, pancreas, and adrenal glands, produce non-tropic hormones. Those released from the pituitary gland in the brain include:
Due to negative feedback on the hypothalamic–pituitary-adrenal (HPA) axis, administration of exogenous glucocorticoids such as prednisone and dexamethasone suppress the secretion of adrenocorticotropic hormone (ACTH) from the pituitary gland and the production of cortisol from the adrenal glands, resulting in adrenal suppression and atrophy and, upon discontinuation of the glucocorticoid, temporary adrenal insufficiency. Similarly, albeit relatively weakly, CPA has the ability to reduce ACTH and cortisol levels and produce adrenal gland shrinkage, as well as, upon discontinuation, adrenal insufficiency, in both animals and humans, indicating that it possesses weak glucocorticoid properties. Paradoxically however, "in vitro", CPA is an antagonist of the glucocorticoid receptor (GR) and a suppressor of adrenal cortisol and corticosterone production by inhibiting the enzymes 3β-hydroxysteroid dehydrogenase and 21-hydroxylase, which are antiglucocorticoid actions. This paradox may be explained by the fact that certain active metabolites of CPA, such as its major metabolite 15β-hydroxycyproterone acetate (which is present at serum levels approximately twice those of CPA in humans), are, contrarily, agonists of the GR, and it can be assumed that their glucocorticoid actions overall significantly outweigh the simultaneous antiglucocorticoid actions of CPA. Both cyproterone and CPA, via their metabolites, have been found to possess glucocorticoid effects, and based on studies in mice, it has been suggested that CPA has approximately 1/5th the potency of prednisone as a glucocorticoid.
Mutations in the "NR0B1" gene located on the X chromosome (Xp21.3-p21.2) cause X-linked adrenal hypoplasia congenita. The "NR0B1" gene provides instructions to make a transcription factor protein called DAX1 that helps control the activity of certain genes. When the "NR0B1" gene is deleted or mutated, the activity of certain genes is not properly controlled. This leads to problems with the development of the adrenal glands, two structures in the brain (the hypothalamus and pituitary gland), and reproductive tissues (the ovaries or testes). These tissues are important for the production of many hormones that control various functions in the body. When these hormones are not present in the correct amounts, the signs and symptoms of adrenal insufficiency and hypogonadotropic hypogonadism can result. This condition is inherited in an X-linked recessive pattern."This article incorporates public domain text from The U.S. National Library of Medicine"
The adrenal gland secretes a number of different hormones which are metabolised by enzymes either within the gland or in other parts of the body. These hormones are involved in a number of essential biological functions.[23]
The adrenal arteries are arteries in the human abdomen that supply blood to the adrenal glands.
The adrenal glands are named for their location relative to the kidneys. The term "adrenal" comes from ad- (Latin, "near") and renes (Latin, "kidney").[51] Similarly, "suprarenal", as termed by Jean Riolan the Younger in 1629, is derived from the Latin supra (Latin: "above") and renes (Latin: kidney). The suprarenal nature of the glands was not truly accepted until the 19th century, as anatomists clarified the ductless nature of the glands and their likely secretory role – prior to this, there was some debate as to whether the glands were indeed suprarenal or part of the kidney.[50]
In the early gestational period, the weight of the adrenal glands outweighs even the metanephric kidneys and is comparatively a larger organ. After the 10th week of gestation, the kidney grows at a much rapid rate than the adrenal glands. Hence with an increase in gestational time, i.e. by the 12th week of gestation, both the kidneys and adrenal glands measure the same. Post 12 weeks the kidneys measure more than the adrenal glands. However, the Adrenal gland is a larger organ in the fetus than the adult. The same group of researchers further observed that with the increase of fetal age, the adrenal glands also weigh more as observed by the research group in 90 human fetuses. However, the rate of increase is not uniform and varies throughout the fetal growth like other organs.
Zacopride was found to significantly increase aldosterone levels in human subjects for 180 minutes at a dose of 400 micrograms. It is thought to do this by stimulating the 5-HT receptors on the adrenal glands. Zacopride also stimulated aldosterone secretion when applied to human adrenal glands "in vitro". No significant changes were observed in renin, ACTH, or cortisol levels.
Cortisol is produced in the human body by the adrenal gland in the zona fasciculata, the second of three layers comprising the adrenal cortex. The cortex forms the outer "bark" of each adrenal gland, situated atop the kidneys. The release of cortisol is controlled by the hypothalamus, a part of the brain. The secretion of corticotropin-releasing hormone by the hypothalamus triggers cells in the neighboring anterior pituitary to secrete another hormone, the adrenocorticotropic hormone (ACTH), into the vascular system, through which blood carries it to the adrenal cortex. ACTH stimulates the synthesis of cortisol and other glucocorticoids, mineralocorticoids, and dehydroepiandrosterone.
The adrenal glands are located on both sides of the body in the retroperitoneum, above and slightly medial to the kidneys. In humans, the right adrenal gland is pyramidal in shape, whereas the left is semilunar or crescent shaped and somewhat larger.[8] The adrenal glands measure approximately 3cm in width, 5.0cm in length, and up to 1.0cm in thickness.[9] Their combined weight in an adult human ranges from 7 to 10grams.[10] The glands are yellowish in colour.[8]
Thehuman genomeincludes approximately 20,000 protein coding genes and 70% of thesegenes are expressedin the normal, adult adrenal glands.[35][36]Only some 250 genes are more specifically expressed in the adrenal glands compared to other organs and tissues.The adrenal gland specific genes with highest level of expression include members of the cytochrome P450 superfamily of enzymes. Corresponding proteins are expressed in the different compartments of the adrenal gland, such as CYP11A1, HSD3B2 and FDX1 involved in steroid hormone synthesis and expressed in cortical cell layers, and PNMT and DBH involved in noradrenalin and adrenalin synthesis and expressed in the medulla.[37]