endocrine disorders Flashcards
endocrine system functions
- contributes to processes involved in maintaining physiological equilibrium (homeostasis)
- includes all tissues or glands that secrete hormones into the blood
- hormones bond to specific receptors that allows the hormone to exert its effect
- > delivered to many tissues, but will ONLY affect those with the appropriate receptor
- > nervous system: neutrotransmitters, neurohormone
- > endocrine sysytem: hormones
- secretion of most hormones is regulated by a negative feedback system
negative feedback
- primary mechanism through which the endocrine system maintains homeostasis
- secretion of specific hormones are turned “on” or “off” by specific physiological changes - like thermostat
- ex: plasma glucose levels and the insulin/glucagon response - eating raises blood glucose, pancreas releases insulin
why is the hypothalamus so important
- “master gland”
- major link between nervous and endocrine system
pituitary attached to hypothalamus by [ ]
- by infundibulum
- pituitary has 2 parts
1. posterior pituitary: storage site for 2 hormones
2. anterior pituitary: synthesis and release
what does the hypothalamus do
- synthesizes and secretes “regulatory” hormones
* releasing hormones: stimulate release of anterior pituitary hormones
* release inhibitory hormones: inhibit release of anterior pituitary hormones
* “directs” pituitary gland (hypophysis) - synthesizes 2 hormones that are stored in posterior pituitary
* oxytocin - the love hormone
* vasopression (also called antidiuretic hormone (ADH))
releasing hormones
- regulatory hormone from hypothalamus
- stimulate release of anterior pituitary hormones
release inhibitory hormones
- regulatory from hypothalamus
- inhibit release of anterior pituitary hormones
hormones stored in posterior pituitary
- oxytocin and vasopression/ADH
- synthesized by hypothalamus
hypothalamus and anterior pituitary
- hypothalamus produces releasing and inhibiting hormones
- hypophyseal portal system: connect hypothalamus to pituitary
secretory hypothalamus
- hypothalamus synthesizes and secretes a variety of regulatory hormones
- hypothalamic releasing/inhibitory factors act upon anterior pituitary
- direct relase of anterior pituitary hormones
- hypothalamus can release GHRH (growth hormone releasing hormone) and SS (somatostatin/GH inhibitory hormone)
hypophyseal portal system
hypothalamic releasing hormones and effects on pituitary
- corticotropin releasing hormone (CRH): stimluates adrenocorticotropic hormone (ACTH) secretion
- thyrotropin releasing hormone (TRH): stimulates thyroid stimulating hormone (TSH) and prolactin
- growth hormone releasing hormone (GHRH): stimualtes growth hormone (GH) secretion
- somatostatin (growth hormone-inhibiting hormone [GHIH]): inhibits GH secretion
- gonadotropin releasing hormone (GnRH/LHRH): stimulates LH and FSH secretion
- prolactin releasing hormone (PRH): stimulates prolactin secretion
- prolactin inhibiting hormone (dopamine): inhibits prolactin secretion
pituitary disorders
- pituitary tumors account for ~10-15% of intracranial tumors
- majority are an adenoma - a benign tumor
- pituitary close proximity to optic nerve: changes in vision, HA, nausea
what happens in pituitary disorders
- result in too much or too little hormone release
- hyperpituitarism
- > acromegaly/gigantism (increased growth hormone)
- > Cushing’s disease (increased cortisol) - syndrome in adrenals
- hypopituitarism
- > diabetes insipidus (decreased vasopression [ADH]): like DM but no change in normal blood glucose
- common symptoms
- HA, vision changes, lethargy/fatigue, nausea and vomiting, nasal drainage, behavioral changes (hostility, depression), changes in sense of smell
growth hormone (GH) disorders
- gigantism: excessive secretion of GH in children, epiphyseal plate not yet closed
- acromegaly: excessive secretion of GH in adults, most often in 4th decade, slow but continuous progression (andre the giant)
posterior pituitary (neurohypophysis)
- stores releases 2 hormones
1. ADH (vasopressin): anti-diruetic hormone - increases BP
2. oxytocin
vasopressin (anti-diretic hormone [ADH])
- regulates blood volume/pressure and salt concentration (plasma osmolarity)
- cells of supraoptic and paraventricular nuclei are osmoreceptors - how much water
- posterior pituitary secretes vasopressin (ADH) in response to:
- > reduced blood volume (baroreceptors sense low BP)
- > increased plasma osmotic pressure (osmoreceptors in the hypothalamus sense increased solute in blood)
does ADH increase or decrease during happy hour
- goes down - pee a lot
diabetes insipidus (DI)
- loss of ADH production
- no issue with glucose metabolism
- characterized by excretion of large volume of urine (polyuria - low BP) and excessive thirst (polydipsia) and increased appetite (polyphagia)
- 2 causes
1. posterior pituitary doesn’t secrete ADH - central/neurogenic DI
2. insensitivity of kidney to ADH - nephrogenic DI
diagnosis and symptoms of diabetes insipidus (DI)
- diagnosis
- NO hyperglycemia
- dilute urine
- blood test: hypernatremia and increased plasma osmolality
- signs and symptoms
- 3 Ps: polydipsia, polyuria, polyphagia
- hypovolemia and dehydration: dizziness, hypotension, seizures
- muscle weakness/fatigue
adrenal disorders
- hyperfunction
- Cushing’s disease/syndrome
- hyperaldosteronsim (Conn’s syndrome)
- pheochromocytoma
- hypofunction
- hypoaldosteronism/hypocortisolism (Addison’s disease)
cortisol
- normally, release of cortisol is controlled by the hypothalamus:
- hypothalamus secretes corticotropin-releasing hormone (CRH)
- CRH triggers the anterior pituitary to secrete adrenocorticotropic hormone (ACTH) into the vascular system
- ACTH is carried in the blood to the adrenal cortex stimulating the synthesis of cortisol
- pituitary tumors: hyper ACTH – hyper-cortisol (hyperglycemia, osteoporosis, muscle fatigue)
normally, as cortisol synthesis increases, what happens to CRH production
goes down
common functions of cortisol
- counter-regulatory to insulin: promotes hyperglycemia
- decreases bone formation (decreased osteoblast function) and decreases intestinal Ca++ absorption
- acts as a diuretic
- influences immune function: inhibits production/release of inflammatory mediators
osteoblasts vs osteoclasts
- osteoblasts build bone
- osteoclasts eats up bone
cushing’s disease/syndrome
- hypersecretion of cortisol
- cushing’s disease - pituitary cushing’s (CNS)
- cushing’s syndrome - adrenal cushing’s (kidney)
cushing’s disease
- pituitary cushing’s - CNS
- pituitary adenoma: secretes ACTH
- ACTH dependent: “disease”
cortisol hypersecretion
cushing’s syndrome
- adrenal cushing’s - kidney
- adrenal adenoma: secretes cortisol
- exogenous corticosteroids: most common
- iatrogenic cushing’s syndrome - due to medical provider
- ACTH independent: “syndrome”
cortisol hypersecretion
cushing’s disease/syndrome - symtpoms
cortisol hypersecretion
- central obesity
- rapid weight gain with sparing of limbs
- fat redistribution: moon face, buffalo hump
- skin
- thinning of skin and capillary fragility - easy bruising
- striae
- poor wound healing
- muscle wasting and weakness
- tachycardia, hypertension
- osteoporosis
- impaired GI Ca2+ absorption (antagonizes vitamin D)
- hyperglycemia/DM
- “stress response”
- immunosuppression and increased infection risk
treatment of cushing’s disease/syndrome
- depends on reason for excess cortisol
- tumor removal: disease (pituitary tumor excision via trans-sphenoidal surgery), sydrome (adrenal tumor excision - adrenalectomy)
- iatrogenic: decrease corticosteroids dosing if possible
thyroid gland and function
- thyroid follicles produce thyroid hormones (thyroxine T4 and triiodothyronine T3 - ratio is 15:1)
- T4 is a pro-hormone and is converted to active T3 (“the” thyroid hormone)
- iodine necessary for formation of T4 and T3 - goiter is overgrowth of thyroid due to iodine deficiency
- functions
- increase basal metabolic rate (BMR)
- important for brain and muscular development
- CV: increases HR/contractiltiy and cardiac output
- CNS: arousal states
thyroid produces calcitonin
- calcitonin is produced in response to hypercalcemia - calcitonin decreases serum Ca2+
- calcitonin opposes parathyroid hormone (PTH) - PTH increases serum Ca2+