Pituitary Study Notes Introduction - adenohypophysis produces ACTH, TSH, FSH, LH, GH, and prolactin; if the input from the hypothalamus is interrupted, the adenohypophsis makes more prolactin and less of everything else - hyperpituitarism is defined to mean too much of one of the hormones from the adenohypophysis - hypopituitarism (Simmond's disease) is defined to mean loss of one or more of the hormones from the adenohypophysis; need to lose about 75% of the adenohypophysis before any clinical changes occur - neurohypophysis (posterior pituitary) is composed of the axons of the hypothalamic neurons; pituicytes are modified glial elements; you notice Herring bodies here, composed of ADH awaiting release Anterior Lobe Adenomas - pituitary adenomas constitute 10% of all diagnosed primary intracranial tumors - more common in pts with autosomal dominant multiple endocrine neoplasia I syndrome - pituitary adenomas typically present as one or more of the following: 1) endocrine problems, both from hormones produced by the tumor itself and from damage to the rest of the adenohypophysis and/or neurohypophysis 2) visual problems, from an expanding mass impinging on the optic chiasm 3) enlarged sella turcica on skull X-rays, again due to expanding masses 4) least often, signs of increased intracranial pressure - large pituitary adenomas eventually erode the sella, clinoid process, diaphragma sellae, optic nerves and chiasm, and even the cavernous sinuses, nasal, sinuses, or brain - hemorrhages into a large pituitary adenoma can produce pituitary apoplexy, which can simulate a berry aneurysm rupture - acidophilic adenomas typically make growth hormone and/or prolactin - basophilic adenomas typically make ACTH; less often, they make TSH or the gonadotrophins - chromophobe adenomas typically make prolactin or nothing - frequencies of production of various hormones by pituitary tumors: - prolactin - 30% -men: impotence, loss of libido -women: amenorrhea, glacatorrhea, infertility - both: obesity - growth hormone 20% - children: giantism - adults: acromegaly - GH + prolactin 10% - growth hormone effects dominate - ACTH 15% - Cushing's disease - LH, FSH 25% - most are silent until mass effect or autopsy makes known - TSH rare hyperthyroidism - hyperprolactinemia - real functioning prolactinomas in women generally declare themselves while quite small; other casues are hypothalamic tumors and anti-dopamine drugs - the treatment of choice for prolactinemia is the dopamine receptor agonist bromocriptine with or without surgery - giantism and acromegaly - excess growth hormone before puberty produces excessively tall stature; people were typically crippled by nerve, muscle, and joint problems, acquired acromegalic features as they got older, and died of young complications of their diabetes - excess growth hormone after puberty produces acromegaly - the typical acromegalic has a huge jaw, develops a deep gutteral voice, gets oily skin, gets joint deformities, and suffers from secondary diabetes - most pituitary giants and acromegalic pts have a pituitary macro-adenoma; the best treatment is surgical adenoma - Cushing's disease - implies production of ACTH by a pituitary tumor, usually a small microadenomas, usually not enough ACTH production to darken the skin - most cases of idiopathic adrenal hyperplasia are really due to ACTH-omas - secondary hyperthyroidism - mysteriously, TSH-producing adenomas of the pituitary gland are rare - piuitary resistence to thyroid hormone isn't well-understood; pts have excess hTSH and become hyperthyroid Panhypopituitarism - symptoms are highly variable - growth hormone slows body wasting that occurs in old age - adults lacking GH have more fat and less muscle - loss of gonadotropins produce loss of libido and body hair - loss of prolactin prevents lactation, which would only be noticed after childbirth - loss of thyrotropin produces secondary hypothyroidism - loss of ACTH produces secondary adrenal insufficiency , which is just as deadly as primary adrenal insufficiency - if the posterior pituitary gland is involved, loss of ADH produces pituitary diabetes insipidus - pts with hypopituitarism are usually prone to precocious atherosclerosis - most of the time, hypopituitarism is due to: 1) destruction of the pituitary by a pituitary adenoma, surgery, radiation, or trauma 2) Sheehan's pituitary necrosis 3) the empty sella syndrome - Sheehan's pituitary necrosis - occurs when shock complicates a problem delivery - the drop in BP results in inadequate blood supply to the gland, which is already hyperplastic and has its vessels squezed half-shut - less often, piuitary necrosis results from sickle-cell disease, temporal arteritis, or trauma - usually the gonadotropins and prolactin are the most decreased - the typical Sheehan's pt fails to lactate or resume menstruating after dleivery - when necrosis is less complete, the disease tends to progress as the remaining cells are entrapped in scar tissue - the empty sella syndrome classically results from slow crushing of the gland by CSF pressure when the hole in the diaphragma sellae is wide enough to allow arachnoid to herniate intothe sellae; some pts develop pituitary insufficiency Pituitary Dwarfism - failure to produce normal amounts of growth hormone in childhood results in miniature, well-proportioned people; causes range from idiopathic to various genetic syndromes to other causes of hypopituitarism - around 50% of idiopathic dwarves are breech or transverse deliveries, and the damage to the hypothalamic-piuitary axis may occur when their little skulls get crunched - pygmies have tissues that do not respond well to growth hormone; some people call this pituitary dwarfism type II - if thyrotropin is normal or thyroid hormone is replaced, the children will be of normal intelligence - if gonadotropin production is normal or sex steroids are administered, puberty should occur normally Craniopharyngioma - this is a benign tumor of Rathke's pouch remnants which generally occurs just above the pituitary and sella turcica; it is locally agressive but does not metastasize; the optic nerves and chiasm, and then hypothalamus, are damaged - microscopically the tumor generally recalls developing tooth enamel, with areas of columnar cells, stellate mesenchyme, usually calcification, sometimes stratified squamous stuff and/or bone Diabetes Insipidus - because the posterior pituitary gland is really processes of hypothalamic neurons, a variety of processes can damage it - remember - 1) causes within the sella - compression by pituitary adenoma, pituitary infarction from any cause, pituitary abalation, and sarcoidosis; 2) causes above the sella - old bacterial meningitis, damage from encephalitis, meningeal tuberculosis, hypophyseal glioma or germinoma, craniopharyngioma, metastatic cancer, or skull trauma - also remember nephrogenic diabetes insipidus, the inability of the kidney to respond to ADH - there are two posterior pituitary gland tumors - pituitcytomas are astrocytomas arising from the pituicytes - the granular cell tumor resembles similar tumors of Schwann cell origin seen elsewhere Syndrome of Inappropriate ADH Production - pts have continuous ADH production unrelated to plasma osmolality - water leaks back freely from the collecting ducts, the blood becomes hypotonic, and the pt loses the ability to produce dilute urine - low blood tonicity leads to seizures and then to death - the syndrome is almost always due to ectopic ADH production by a tumor; pituitary problems almost never produce inappropriate ADH - the best treatment is to make the inappropriate ADH appropriate by restricing water Pituitary-Hypothalamic Sydromes - these result from abnormal function of the hypothalamus, reflected in problems with sexual development - Froehlich's syndrome is hypothalamic hypogonadism plus obesity; affected boys are obese, show a female pattern of fat distribution, and have delayed appearance of primary or secondary sex characteristics - the problem in adiposogenital dystrophy may be in the hypothalamus; it could also be constitutional without a demonstrable hypothalamic lesion - endocrine disease is especially worthy of your serious attention because 1) it is prevalent; 2) it is generally very treatable; 3) if you diagnose it incorrectly, you doom the patient to lifelong medication; 4) if you miss it, you doom the pt to long-term ill health and probably mental illness; 5) many cases of endocrine disease get missed for a long, long time