Pituitary Gland Flashcards
What is the pituitary gland?
The pituitary gland is a gland that sits in the hypophyseal fossa, a depression in the sella turcica of the sphenoid bone. The pituitary gland is divided into an anterior part (Adenohypophysis) and a posterior part (Neurohypophysis).
What does the adenohypophysis secrete?
- TSH stimulating the production of thyroid hormones.
- ACTH stimulating the adrenal cortex to produce corticosteroids (aldosterone and cortisol)
- FSH stimulating follicle growth, ovarian estrogen production or sperm production of androgen binding
protein, enabling spermatogenesis and sperm maturation. - LH regulates growth of the corpus luteum or androgen secretion by interstitial cells in the testis.
- GH stimulating growth of skeletal epiphyseal plate and protein production.
- PRL stimulating mammary glands to produce milk.
- MSH stimulating melanocytes
What does the neurohypophysis secrete?
- ADH/vasopressin which stimulates kidneys to reabsorb more water.
- Oxytocin prompting contraction of smooth muscles in reproductive tract ( labor and milk ejection).
What is hypopituitarism? How does in present clinically?
Refers to the a decrease in secretion of pituitary hormones, it can be due to from disease of the gland or the hypothalamus. It occurs when 75% of the parenchyma is lost. The main causes are tumors, traumatic brain injury, pituitary apoplexy, hypothalamic lesions and ischemic necrosis.
Clinically it varies depending on the specific hormone lacking :
- Gonadotropin deficiency : In women presents as oligomenorrhea/amenorrhea, loss of libido, vaginal
dryness or dyspareunia and loss of secondary sex characteristics. In men instead as loss of libido, erectile
dysfunction, infertility, loss of secondary sex characteristic, atrophy of the testis and gynecomastia. - ACTH deficiency : Results in hypocortisolism presenting as malaise, anorexia, weight loss, GI disturbances and hyponatremia.
- TSH deficiency : Very rare cause of hypothyroidism presenting with atrophic thyroid glands.
- GH deficiency : In children GH deficiency causes a constitutional growth delay. Instead, in adults it is mainly asymptomatic, causing fatigue, decreased exercise tolerance, abdominal obesity and loss of
muscle mass. - Prolactin deficiency: failure of postpartum lactation.
What is hyperpituitarism?
When your pituitary gland is overactive, it releases excessive amounts of certain types of pituitary hormones into your bloodstream. A benign tumor in the gland, called a pituitary adenoma, is usually the cause of this condition. An overactive pituitary gland can cause a variety of disorders that affect growth, metabolism, reproduction and other vital body functions.
What are pituitary adenomas?
They are slow growing benign epithelial tumors associated to increased or decreased hormone secretion. They are well circumscribed, encapsulated and non infiltrative. There are some cases in which it lacks a capsule and does infiltrate neighboring tissue, referred to as invasive adenoma. Histologically they are composed of polygonal cells.
What is a prolactinoma?
Prolactinoma is the most common functional pituitary tumor.
Morphologically, prolactinomas are comprised of chromophobic cells expressing PIT-1 juxtanuclearly. Prolactin presence is demonstrated using immunohistochemistry. Lactotroph adenomas have the propensity to undergo dystrophic calcification, ranging from isolated psammoma bodies to extensive calcification of virtually the entire tumoral mass (“pituitary stones”). Clinically, it presents as galactorrhea, amenorrhea and hirsutism in women and as impotence, gynecomastia and visual field defects in men.
What are GH tumors?
They are the second most frequent tumors of the pituitary gland. If the tumor arises in childhood, there will be gigantism since it occurs before the closure of epiphyseal growth plates of long bones. On the other hand, in the adult, it causes acromegaly. Morphologically, densely granulated adenomas are composed of monomorphic acidophilic cells that have strong GH reactivity on immunohistochemistry. Clinical presentation ranges from diabetes mellitus, hypogonadism, large hands and feet, large head.
What are ACTH adenomas?
ACTH producing adenomas leads to adrenal hypersecretion of cortisol and development of Cushing syndrome. Morphologically, these tumors are most often basophilic.
Pathology of the posterior pituitary gland?
Diabetes insipidus : Is a disease in which there is a deficiency in the production of ADH presenting as polyuria and polydipsia due to progressively increasing sodium concentration. If patients fail to compensate for the water loss, they will end up facing massive dehydration. Diabetes insipidus can be central, in case of insufficient or absent ADH secretion, or nephrogenic, when ADH is normally produced but cannot act at the renal level.
