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Endocrine System

hormones that act on cells distant from site of synthesis
increased activity of target tissue down regulates activity of gland (feedback inhibition)

hormone classification

based on nature of their receptors

lactotroph

prolactin (PRL)
mammary glands (production of milk)
produced by anterior pituitary gland

somatotroph

secrete growth hormone
somatomedins: stimulate growth
produced by anterior pituitary

corticotroph

synthesize pro-opiomelanocortic (POMC), which splits into:
corticotropin (ACTH)
b-lipotrophin
anterior pituitary

thyrotrophs

produce thyrotropin (TSH)
anterior pituitary

hyperfunction of pituitary gland

excess production of anterior pituitary hormones is most often caused by anterior pituitary adenoma

classification of adenomas

functional=pt will have symptoms
silent=pt will have no symptoms

anterior pituitary adenoma

3% of cases are associated with MEN1
macroadenoma
microadenoma
common genetic alteration associated with adenoma (GNAS1 gene)
10% of cranial neoplasms

prolactinoma

hyperprolactinemia
chromophobic
small microadenomas to large, expansile tumor
large, nonfunctional until size increased and starts compressing other brain structures

ameonorrhea, galactorrhea, loss of libido, infertility

hyperprolactinemia

women: ammenorrhea, galactorrhea, infertilitiy
men: loss of libido, galactorrhea
sign: peripheral vision loss
causes: hypothalmic lesions, meds, hypothyroidism

Somatotropic adenoma aka growth hormone adenoma

2nd most common pituitary tumor
40% have activating mutations in the GNAS1 gene on chromosome 20q13
hypersecretion of GH
acidophilic
hyperproduction of somatomedins (somatomedin C)

gigantism, acromegaly, impaired glucose tolerance, diabetes mellitys

growth hormone excess

abnormal glucose tolerance
generalized muscle weakness
hypertension
arthritis
osteoporosis
congestive heart failure
clinical: gigantism
acromegaly

gigantism

hypersecretion of growth hormone prior to closure of growth plate

acromegaly

hypersecretion of growth hormone after the closure of growth plates
enlarged jaw (pronathism), sausage fingers

corticotropic adenoma

small at time of dx
hypersecretion of ACTH (stimulates adrenal gland to produce cortisol)
cushings disease/syndrome
hyperpigmentation

cushings disease/syndrome

disease: pituitary adenoma-ACTH hypersecretion
basophilic (mostly)
sometimes multiple microadenomas
syndrome: increased cortisol due to any cause

symptoms of cushings

buffalo hump
hypertension
thinning of skin
moon face with red cheeks
increased abdominal fat
osteoporosis
increase susceptibility to obesity
apple like appearance
could be misdiagnosed as a psych condition

anterior pituitary hypofunction

hypopituitarism
congenital or acquired
causes: non-secretory pituitary adenomas
ischemia necrosis of pituitary (sheehan syndrome)
ablation of the pituitary by surgery or radiation

growth hormone deficiency

pituitary dwarfism
gonadotropin or gonadotropin realeasing hormone deficiency
adults
symptoms: loss of libido, ammenorrhea, loss of secondary sex characteristics, infertility, increased insulin sensitivity

deficiency of ACTH

secondary adrenal failure: no hyperpigmentation of skin
lack of ACTH & beta melanocyte stimulating hormone; hypopigmentation
primary adrenal failure: failure of gland itself
increase of ACTH & beta melanocyte hormone; hyperpigmentation

posterior pituitary

nuerohypophysis
modified glial cells & axonal processes from erve cell bodies in supraoptic and paraventricular nuclei of hypothalamus
hormones: synthesized in hypothalamus neurons
stored and transported via axons to post. pit.
oxytocin
ADH

oxytocin

smooth muscle contraction
uterus, lacterious ducts

ADH

water reabsorption by collective tubules of kidney; antidiuretic

SIADH

Syndrome of Inappropriate Antiduretic Hormone
most common is from secretion from an ectopic source:
tumors, retention of H20, increase in total body water
Na levels decrease
cerebral edema and neurologic impairment

deficiency of ADH

diabetes insipidus-central vs. nephrogenic
central: ADH not being released by pituitary
nephro: kidney tissue not recognizing ADH even though it is being secreted properly by pituitary
causes: trauma, tumors, inflammatory process, surgical procedures
polyuria & thirs due to excreting large amounts of diluted urine

thyroid hormones

thyroxine (T4)
triiodothyronine (T3)
both bound to thyroid binding globulin (TBG)
iodine required for synthesis of thyroid hormone
thyroglobulin: storage
TSY (thyrotropin) feedback

goiter

impaired synthesis of thyroid hormone
rise in TSH causes hypertrophy and hyperplasia of thyroid follicular cells
gross enlargement of thyroid gland
size of goiter is proportional to severity/length of thyroid deficit
capable of producing T4, T3

causes of goiter

physiologic enlargement: puberty, pregnancy
iodine deficiency
hasimoto's thyroiditis
Dyshormonogenesis: failure of thyroid hormone synthesis

types of goiter

toxic goiter: hyperthyroidism (plummer syndrome) hyperfunctioning toxic nodule, no eye bulging, no dermatopathy
nontoxic goiter (diffuse): euthyroid or hypothyroid. diffuse grave's disease; eye bulging
endemic goiter (diffuse): iodine deficient. directly related to iodine deficiency

Thyroid neoplasms

folicular adenomas
papillary carcinoma
medullary cancer
anaplastic carcinoma

thyrotoxicosis (hyperthyroidism)

hpermetabolic state and overactivity of sympthetic nervous system
heat intolerance, weight loss, increased appetite, diarrhea, restless, irritable, proximal muscle weakness, tremors, tachycardia, wide staring gaze, small scant menses, thin hair

grave's disease (diffuse toxic hyperplasia)

thyrotoxicosis
infiltrative opthalmopathy
infiltrative dermopathy
women 7x>men
genetic component
autoimmune
diffuse hyperplasia of thyroid (smooth and symmetric)
opthalmology (wide staring gaze and lid lag): increased adipose tissue behind the orbital space
pretibial edema

hypothyroidism

intrinsic abnormailty in the thyroid or results from hypothalamic or pituitary disease
cretinism (infancy/early childhood)
myxedema (adolescents/adulthood)

cretinism

infancy/early childhood
iodine deficiency
deficiency of enzymes to synthesize thyroid hormones
failure of fetal thyroid to descend from origin
anti-thyroid antibodies from mother to fetus
impaired development of skeleton and nervous system

myxedema

women>men
generalized apathy and mental sluggishness
cold intolerance
weight gain
deepened voice
constipation
menorrhagia
dry skin
hair loss
hypoactive deep tendon reflexes

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