The pituitary gland is a small gland located at the base of the brain that regulates several important bodily functions. It is divided into anterior and posterior lobes. The anterior lobe secretes hormones that control other endocrine glands and regulate processes like growth, metabolism, and reproduction. These include growth hormone, thyroid stimulating hormone, and adrenocorticotropic hormone. The posterior lobe stores and releases oxytocin and vasopressin, which are produced in the hypothalamus and help regulate water balance and milk release. Disorders of the pituitary can impact hormone levels and cause wide-ranging symptoms.

1. PITUITARY GLAND

2. TABLE OF CONTENTIntroduction of Pituitary Gland.Origin and location of Pituitary Gland.Anatomy and Histology of the Pituitary GlandStructure of Pituitary Gland.Parts of Pituitary Gland.Hormones sereted from Pituitary Gland.Diseases found in Pituitary Gland.DiagramsFunctions of Pituitary Gland.Conclusion.

3. Introduction of 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 (0.02 oz.).

4. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity (sella turcica) covered by a dural fold (diaphragm sellae).

5. The pituitary fossa, in which the pituitary gland sits, is situated in the sphenoid bone in the middle cranial fossa at the base of the brain.

6. The pituitary gland secretes hormones regulating homeostasis, including tropic hormones that stimulate other endocrine glands.

7. It is functionally connected to the hypothalamus by the median eminence via a small tube called the Pituitary Stalk.

8. It is considered to be the "master gland".

9. Anatomy and physiology of the pituitary gland:The pituitary gland weighs about 0.5 to 1 g and is divided into anterior and posterior lobes. The pituitary gland sits in the sella turcica immediately behind the sphenoid sinus. Cavernous sinuses are located laterally on each side of the sella, inclusive of the internal carotid artery and cranial nerves III, IV, V1, V2 and VI. Magnetic resonance imaging (MRI) is the best method for the visualization of hypothalamic-pituitary anatomy, because the optic chiasm, vascular structures, and tumor extension to cavernous sinuses can be well visualized compared with other imaging techniquesAnterior pituitary hormones are regulated by hypothalamic releasing and inhibitory hormones and negative feedback action of the target glandular hormones at the pituitary and hypothalamic levels ( Table 1 ). Among pituitary hormones, only the secretion of prolactin is increased in the absence of hypothalamic influence, because it is mainly under tonic suppression by dopamine, the main prolactin inhibitory factor. All anterior pituitary hormones are secreted in a pulsatile fashion and tend to follow a diurnal pattern.

10. Table 1: Relationship Among Hypothalamic, Pituitary, and Feedback Hormones and Target GlandsACTH, adrenocorticotropic hormone; ADH, antidiuretic hormone; CRH, corticotropin-releasing hormone; E2, estradiol; GHRH, growth hormone–releasing hormone; IGF-1, interleukin growth factor 1; LHRH, luteinizing hormone–releasing hormone; PIF, prolactin release inhibitory factor; SMS, somatostatin; T, testosterone; T3, triiodothyronine; T4, thyroxine; TRH, thyrotropin-releasing hormone.Antidiuretic hormone (ADH, vasopressin) is produced by the supraoptic and paraventricular nuclei of the hypothalamus and travel in the axons through the pituitary stalk to the posterior pituitary gland. The chief physiologic stimulus of ADH secretion is an increase in serum osmolality and a decrease in plasma volume, resulting in water reabsorption at the level of the distal collecting ducts of the kidneys. Small increments in serum osmolality, more than 290 mOsm/kg, lead to a prompt secretion of ADH.

12. Origin and location of Pituitary Gland:The pituitary gland is also called The Hypophysis, is the smallest endocrine gland.

13. Hypophysis (meaning undergrowth) is so named because of its location below the brain as undergrowth.

14. This is an unpaired small ovoid gland and is no longer than the end of the little finger.

15. It is located at the base of the brain and lies below the diencephalon in a depression of basis phenoidboneof the skull called Sella Turcica.

16. It is a complex structure formed of ectodermic growth of the mouth cavity and down growth of the infandibulum.Structure of Pituitary Gland:Structurally, the pituitary gland is divided into a larger frontal region (adenohypophysis) and a smaller posterior region (neurohypophysis).

17. The gland is connected to a region of the brain called the hypothalamus by the pituitary stalk. Directly above the pituitary gland and in front of the pituitary stalk are the crossing fibers of the optic nerves, called the optic chiasm.

18. On each side of the pituitary gland is the cavernous sinus. Through each cavernous sinus runs a carotid artery that carries blood to the brain, and important nerves that control eye movements.

19. Because of the close proximity of the pituitary gland to major intracranial nerves and blood vessels, as well as the vital hormonal control the pituitary gland provides, disorders of the pituitary can cause a wide spectrum of symptoms, both hormonal and neurological.Pituitary Gland

20. Parts of Pituitary Gland:Pituitary gland is divided into 3 parts:PITUITARY GLANDAnterior pituitary (Adenohypophysis)Posterior pituitary (Neurohypophysis)Pars Intermedia

21. Anterior pituitary (Adenohypophysis):A major organ of the endocrine system, the anterior pituitary, also called the adenohypophysis, is the glandular, anterior lobe of the pituitary gland.

22. The anterior pituitary regulates several physiological processes including stress, growth, and reproduction.

23. Its regulatory functions are achieved through the secretion of various peptide hormones that act on target organs including the adrenal gland, liver, bone, thyroid gland, and gonads.

24. The anterior pituitary itself is regulated by the hypothalamus and by negative feedback from these target organs.

25. Disorders of the anterior pituitary are generally classified by the presence of over- or underproduction of pituitary hormones.

26. For example, a prolactinoma is a pituitary adenoma that overproduces prolactin. I

27. n Sheehan's syndrome of postpartum hypopituitarism, the anterior pituitary uniformly malfunctions and underproduces all hormones.

28. Proper function of the anterior pituitary and of the organs it regulates can often be ascertained via blood tests that measure hormone levels.AnatomyThe pituitary gland is a pea-sized gland that sits in a protective bony enclosure called the sella turcica. It is composed of three lobes: anterior, intermediate, and posterior. In many animals, these three lobes are distinct. However, in humans, the intermediate lobe is but a few cell layers thick and indistinct; as a result, it is often considered part of the anterior pituitary. In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary.The anterior pituitary is composed of multiple parts:Pars distalis The pars distalis, or "distal part", comprises the majority of the anterior pituitary and is where the bulk of pituitary hormone production occurs. Occasionally, "pars distalis" is incorrectly used as a synonym for the anterior pituitary.[citation needed]

29. Pars tuberalis The pars tuberalis, or "tubular part", forms a sheath extending up from the pars distalis and wrapping around the pituitary stalk. Its function is poorly understood.

30. Pars intermedia The pars intermedia, or "intermediate part", sits between the pars distalis and the posterior pituitary and is often very small in humans. Hormone secretion:The posterior pituitary as a down growth of the brain, it a neurosecretory organ (Wheater, Burkitt & Daniels, 1987).

31. The secretion of hormones from the posterior pituitary is controlled directly by neurons in the hypothalamus (Marieb, 2004).

32. The connecting stalk between the hypothalamus and the lobes of the pituitary gland, the infundibulum, carries the hormones of the posterior pituitary from nuclei in the hypothalamus.

33. The hypothalmicsupraoptic nuclei manufacture anti-diruetic hormone and the hypothalmicparaventricular nuclei manufacture oxytocin.

34. These hormones are then stored in pituitary axons until their release is triggered (Marieb, 2004).

35. The anterior pituitary is a glandular secretory organ (Wheater, Burkitt & Daniels, 1987).

36. The secretion of hormones from the anterior pituitary is controlled by inhibiting and releasing factors secreted by neurons in the hypothalamus.

37. These inhibiting and releasing factors are release into a primary capillary plexus where they travel, via portal veins, to a secondary capillary plexus where they stimulate the glandular tissue of the anterior pituitary to release its hormones.Embryology:The anterior pituitary arises from an invagination of the oral ectoderm and forms Rathke's pouch. This contrasts with the posterior pituitary, which originates from neuroectoderm.

38. Major hormones secreted:

39. Pars Intermedia:Pars intermedia is the boundary between the anterior and posterior lobes of the pituitary.

40. It contains three types of cells - basophils, chromophobes, and colloid-filled cysts.

41. The cysts are the remainder of Rathke’s pouch.

42. In human fetal life, this area produces melanocyte stimulating hormone or MSH which causes the release of melanin pigment in skin melanocytes (pigment cells).

43. However, the pars intermedia is normally either very small or entirely absent in adulthood.In lower vertebrates (fish, amphibians) MSH from the pars intermedia is responsible for darkening of the skin, often in response to changes in background color. This color change is due to MSH stimulating the dispersion of melanin pigment in dermal (skin) melanophore cells.Major hormone secreted:Melanocyte Stimulating Hormone or MSHPosterior pituitary(Neurohypophysis):The posterior pituitary (or neurohypophysis) comprises the posterior lobe of the pituitary gland and is part of the endocrine system. Despite its name, the posterior pituitary gland is not a gland, per se; rather, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary gland.Anatomy:The posterior pituitary consists mainly of neuronal projections (axons) extending from the supraoptic and paraventricular nuclei of the hypothalamus. These axons release peptide hormones into the capillaries of the hypophyseal circulation. In addition to axons, the posterior pituitaryalso contains pituicytes, specialized glial cells resembling astrocytes.Classification of the posterior pituitary varies, but most sources include the three regions below:Pars nervosa Also called the neural lobe or posterior lobe, this region constitutes the majority of the posterior pituitary, and is sometimes (incorrectly) considered synonymous with it. Notable features include Herring bodies and pituicytes.

44. Infundibular stalk Also known as the infundibulum or pituitary stalk, the infundibular stalk bridges the hypothalamic and hypophyseal systems.Hormones secreted:Hormones known classically as posterior pituitary hormones are synthesized by the hypothalamus. They are then stored and secreted by the posterior pituitary into the bloodstream.Role in disease:Insufficient secretion of vasopressin underlies diabetes insipidus, a condition in which the body loses the capacity to concentrate urine. Affected individuals excrete as much as 20 liters of dilute urine per day. Oversecretion of vasopressin causes the syndrome of inappropriate antidiuretic hormone (SIADH).

45. Hormones secreted from Pituitary Gland:HORMONES SECRETED FROM PITUITARY GLANDThyroid Stimulating Hormone (TSH):

46. Stimulates the thyroid gland to release thyroid hormones.

47. Control basal metabolic rate and play an important role in growth and maturation.

48. Affect almost every organ in the body.

49. Growth Hormone (GH): Principal hormone that regulates growth.

50. Adrenocorticotropic Hormone (ACTH): Triggers the adrenal glands, which regulate stress response with the release of hormones such as cortisol and aldosterone.

51. Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH): Control reproduction.

52. Prolactin (PRL): Stimulates secretion of breast milk. Melanocyte-stimulating hormone(MSH):They stimulate the production and release of melanin (melanogenesis) by melanocytes in skin and hair

53. Oxytocin:

54. it is released in large amounts after distension of the cervix and uterus during labor

55. after stimulation of the nipples, facilitating birth and breastfeedingreastfeeding.

56. Recent studies have begun to investigate oxytocin's role in various behaviors, including orgasm, social recognition, pair bonding, anxiety, and maternal behaviors

57. Vasopressin, also called anti-diuretic hormone (ADH): Promotes water retention.

58. ThyroidStimulatingHormone(TSH):Thyroid-stimulating hormone (also known as TSH or thyrotropin) is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid glandRegulation of thyroid hormone levels:TSH stimulates the thyroid gland to secrete the hormones thyroxine (T4) and triiodothyronine (T3).TSH production is controlled by thyrotropin-releasing hormone (TRH), which is manufactured in the hypothalamus and transported to the anterior pituitary gland via the superior hypophyseal artery, where it increases TSH production and release. Somatostatin is also produced by the hypothalamus, and has an opposite effect on the pituitary production of TSH, decreasing or inhibiting its release.The level of thyroid hormones (T3 and T4) in the blood has an effect on the pituitary release of TSH; when the levels of T3 and T4 are low, the production of TSH is increased, and, on the converse, when levels of T3 and T4 are high, TSH production is decreased. This effect creates a regulatory negative feedback loop

60. The TSH receptorThe TSH receptor is found mainly on thyroid follicular cells.Stimulation of the receptor increases T3 and T4 production and secretion.Stimulating antibodies to this receptor mimic TSH and cause Graves' disease.Diagnostic:Further information: Reference ranges for blood tests.Thyroid hormonesTSH levels are tested in the blood of patients suspected of suffering from excess (hyperthyroidism), or deficiency (hypothyroidism) of thyroid hormone. In general, a standard reference range for TSH for adults is between 0.4 and 5.0 µIU/mL (equivalent to mIU/L), but values vary slightly among labs. The therapeutic target range TSH level for patients on treatment ranges between 0.3 to 3.0 μIU/L.The interpretation depends also on what the blood levels of thyroid hormones (T3 and T4) are.TSH levels for children normally start out much higher. In 2002, the National Academy of Clinical Biochemistry (NACB) in the United States recommended age-related reference limits starting from about 1.3 to 19 µIU/mL for normal-term infants at birth, dropping to 0.6–10 µIU/mL at 10 weeks old, 0.4–7.0 µIU/mL at 14 months and gradually dropping during childhood and puberty to adult levels, 0.4–4.0 µIU/mL.The NACB also stated that it expected the normal (95%) range for adults to be reduced to 0.4–2.5 µIU/mL, because research had shown that adults with an initially measured TSH level of over 2.0 µIU/mL had "an increased odds ratio of developing hypothyroidism over the [following] 20 years, especially if thyroid antibodies were elevated"

61. A TSH assay is now also the recommended screening tool for thyroid disease. Recent advances in increasing the sensitivity of the TSH assay make it a better screening tool than free T4

62. Growth Hormone (GH):Growth hormone (GH) is a protein-based peptide hormone. It stimulates growth, cell reproduction and regeneration in humans and other animals. Growth hormone is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by the somatotroph cells within the lateral wings of the anterior pituitary gland. Somatotropin refers to the growth hormone produced naturally in animals, whereas the term somatropin refers to growth hormone produced by recombinant DNA technology,and is abbreviated "HGH" in humans.Growth hormone is used in medicine to treat children's growth disorders and adult growth hormone deficiency. In recent years, growth hormone replacement therapies have become popular in the battle against ageing and obesity. Reported effects on GH-deficient patients (but not on healthy people) include decreased body fat, increased muscle mass, increased bone density, increased energy levels, improved skin tone and texture, increased sexual function, and improved immune system function. At this time, hGH is still considered a very complex hormone, and many of its functions are still unknown.In its role as an anabolic agent, HGH has been used by competitors in sports since the 1970s, and it has been banned by the IOC and NCAA. Traditional urine analysis could not detect doping with HGH, so the ban was unenforceable until the early 2000s when blood tests that could distinguish between natural and artificial hGH were starting to be developed. Blood tests conducted by WADA at the 2004 Olympic Games in Athens, Greece primarily targeted HGH.

63. Structure:The major isoform of the human growth hormone is a protein of 191 amino acids and a molecular weight of 22,124 daltons. The structure includes four helices necessary for functional interaction with the GH receptor. It appears that, in structure, GH is evolutionarily homologous to prolactin and chorionic somatomammotropin. Despite marked structural similarities between growth hormone from different species, only human and primate growth hormones have significant effects in humans.Several molecular isoforms of GH exist in the pituitary gland and are released to blood. In particular, a ~ 20 kDa variant originated by an alternative splicing is present in a rather constant 1:9 ratio,while recently an additional variant of ~ 23-24 kDa has also been reported in post-exercise states at higher proportions.This variant has not been identified, but it has been suggested to coincide with a 22 kDaglycosilated variant of 23 kDa identified in the pituitary gland.Furthermore, these variants circulate partially bound to a protein (growth hormone-binding protein, GHBP), which is the truncated part of the growth hormone receptor, and an acid-labile subunit (ALS).

64. Functions of GH:Main pathways in endocrine regulation of growth.

65. Effects of growth hormone on the tissues of the body can generally be described as anabolic (building up).

66. Like most other protein hormones, GH acts by interacting with a specific receptor on the surface of cells.

67. Increased height during childhood is the most widely known effect of GH. Height appears to be stimulated by at least two mechanisms