Histology Of The Endocrine System Flashcards
Pituitary adenomas
Often produce excess numbers of functional acidophils or basophils
If an adenoma involves somatotropin cells = gigantism in children or acromegaly in adults
Due to excessive GH production
Acromegaly Symptoms
- large beefy tongue
- deep voice
- large hands/feet
- coarse facial features with premature aging lines
- diaphoresis
- early insulin resistance and hypertension
- increased risk for colorectal cancers
Diagnosis =increased serum IGF-1, and failure to suppress serum GH levels following oral glucose test
- also pituitary mass is usually seen on MRI
Treatment:
- resection of tumor
- treat with octeotide/pegvisomant or dopamine agonists
Diabetes insipidus
Central DI = Caused by any damage to the posterior pituitary
- most common = tumors or head trauma
- always shows decreased ADH
- urine becomes concentrated with ADH shots
- treatment = desmopressin and hydration
Nephrogenic DI = hereditary, secondary to hypercalcemia/hypokalemia or lithium use
- ADH can be lowered or normal
- urine DOESNT become concentrated with ADH shots
- treatment = HCTZ/indomethacin/amiloride/salt restriction
BOTH Result in LOWERED levels of vasopressin which produces:
- inability to concentrate urine which produces chronic clear urine
- polyuria
- polydipsia
Addisons disease
Adrenal cortical insufficiency
Any degeneration of the adrenal cortex
- almost always autoimmune based
Results in concomitant loss of glucocorticoids/mineral corticoids and androgens
Most common symptom seen in pheochromocytomas
Blood pressure swings hypertension & hypotension
Caused by periodical release of high levels of catecholamines
Type 1 and 2 diabetes
Both are characterized by a loss of insulin’s effect of cells being able to uptake glucose from blood stream
Type 1: insulin dependent diabetes
- caused by a loss of B-cells in the pancreas often due to autoimmune dysfunction
- treatment = insulin injects
Type 2: insulin independent diabetes
- caused by B-cells not secreting enough insulin and peripheral target cells being “resistant” to insulin effects
- commonly seen in obesity and other comorbidities.
- treatment is much more difficult and varies from person-person
Chronic dietary iodine deficiencies
Chronic deficiency in iodine causes thyroid hormone production to be halted.
This produces thyroid optic cells of the antihero pituitary gland to produce excess TSH in response which leads to hypertrophic thyroid follicles and ultimately enlargement of the overall thyroid gland
- deemed a “goiter”
Hyperthyroidism and hypothyroidism
Hyperthyroidism:
- chronic over production of thyroid hormones
- usually induced by Graves’ disease (autoimmune attack on follicular cells in the thyroid which induces over production)
- most common symptoms = weight loss/nervousness/sweating/heat intolerance
Hypothyroidism:
- chronic under production of thyroid hormones
- usually induced by chronic thyroiditis or inadequate secretion of TSH in the anterior pituitary glans
- most common symptoms: tiredness/weight gain/cold intolerance/ inability to concentrate
both are heavily genetic based
Hypoparathyroidism and hyperparathyroidism
Hypoparathyroidism
- diminished PTH secretion which casues bones to become MORE DENSE and mineralized
- also causes striated muscles to exhibit abnormal contractions due to inadequate calcium ion concentrations
Hyperparathyroidism
- excessive PTH production LESS DENSE bones and stimulates osteoclast number and activity.
- leads to increased levels of blood calcium which can pathologically deposit into arteries and kidneys and other organs
What are corpora arenacea?
Variously sized concentrations of calcium and magnesium salts in the pineal gland
- often deemed “brain sand”
- overall amount increases overtime but serves no known function on the pineal gland
Is often used as a landmark for the midline of the pineal gland
Pituitary gland location
Located within the sella turcica of the sphenoid bone
Blood supply of the posterior pituitary gland (neurohypophysis)
Two branches of the internal carotid artery
1) inferior hypophyseal artery:
- gives rise to the inferior hypophyseal plexus
- supplies the neurohypophysis
- receives ADH and oxytocin and transports these hormones
2) superior hypophyseal artery:
- gives rise to the hypothalamic-hypophyseal portal system
- primary plexus supplies = pars tuberalis and median eminence
- secondary plexus supplies = pars distal is and intermedia. Receives products from the hypothalamus to regulate blood flow
3 parts of the adenohypophysis
1) pars tuberalis
- wraps around the infundibulum stalk and is composed of basophilic gonadotrophs
2) pars intermedia
- adjacent to the pars nervosa and is composed of basophilic corticotrophs/chromophobes/small colloid cysts
3) Pars distalis
- largest component of the adenohypophysis and is the primary functional component
- contains all the hormone secreting cells of the anterior pituitary
Embroyonic origin of the anterior vs posterior pituitary
Neurohypophysis:
- arises as part of the ventral diencephalon
- doesnt actually secrete anything and just contains hypothalamus neurons/projections
- does store ADH and oxytocin however that are produced by cell bodies in paraventricular and supraoptic nuclei of the hypothalamus
- primary cells found physically inside the neurohypophysis is pituicytes which is similar to glial cells of the CNS
- is neural ectoderm derived
Adenophysis
- arises from the invagination of mucosa in the superior surface of the oral cavity via ralthes pouch
- contains all hormone secreting cells which are also ectoderm derived
- also contains mesoderm CT
- is oral ectoderm derived from Rathke’s pouch
Chromophobes
Heterogenous group of early staining cells with almost no secretory granules.
- found in the adenohypophysis
Induces:
- stem cells
- progenitor cells
Acidophillic chromophobes
Identified by pink staining cytoplasmic granules and include two subtypes. Found in the adenohypophysis
1) somatotrophs
- MOST abundant cell type in the anterior pituitary (50%)
- secretes somatotropin (Growth hormone) which acts on all body tissues to stimulate growth
2) Lactotrophs
- secretes prolactin
- acts on mammary glands to promote maturation of secretory glands in breasts
Basophilic chromophils
Identified by blue/purple stains cytoplasmic granules. Found in the adenohypophysis.
Three subtypes exist
1) thyrotrophs
- LEAST abundant cell type
- secretes thyroid stimulating hormone (TSH) which stimulates thyroid hormone release from thyroid
2) corticotrophs
- synthesis protein pro-opiomelanocortin (POMC).
- POMC is cleaved into both adrenocorticotropic hormone (ACTH) and B-lipotropin (B-LPH) which function to stimulate the adrenal cortex release of corticosteroids and promotes lipid metabolism respectively
3) gonadotrophs
- secretes both FSH and LH
- FSH = promotes ovarian follicle development and estrogen secretion in females; stimulates spermatogenesis in males
- LH = promotes ovarian follicle maturation and progesterone in females; promotes androgen secretion in interstitial cells in males
What are the 4 main “releasing”hormones
All act to promote release of other hormones
1) thyrotropin-releasing hormone (TRH)
2) Gonadotropin-releasing hormone (GnRH)
3) Corticotropin-releasing hormone (CRH)
4) Growth hormone-releasing hormone (GHRH)
What are the 2 main “inhibiting” hormones
1) somatostatin
- inhibits release of GH and TSH
2) dopamine
- inhibits release of prolactin
