Metabolic Disorders of the Thyroid and Adrenal Glands Flashcards
what is the largest endocrine gland in the body?
thyroid gland
functional unit of thyroid gland
follicle
follicle base
touches the bloodstream
follicle apex
touches the colloid
thyroid gland produces and secretes…
thyroid hormones
thyroid gland uptakes and stores…
iodine
what is necessary for thyroid hormone production?
iodine
lack of iodine=
iodine deficiency disorders (IDDs)
excess of iodine=
hyperthyroidism
sources of iodine
food (primary source)
medications: amiodarone
thyroid hormones are found…
in entire body
most abundant thyroid hormone
T4- thyroxine
*prehormone
most active thyroid hormone
T3- triiodothryonine
inactive thyroid hormone
rT3- reverse T3
thyroid releasing hormone
secreted by hypothalamus
important in regulation of thyroid hormones
thyroid-stimulating hormone
secreted in pituitary gland
important in regulation of thyroid hormones
thyroglobulin
protein involved in synthesis
thyroid peroxidase
involved in production of thyroid hormones
where is T4 converted into T3 or rT3?
liver & kidney
what converts T4 to T3?
iodothyronine deiodinase enzyme or iodide peroxidase
*contain selenium
selenium deficiency can lead to…
decreased T3 levels
thyroid hormone biosynthesis
- active uptake of IODINE for Na; stimulated by TSH; @ base of follicle
- oxidized to ACTIVE iodine (by thyroid peroxidase)
- active iodine moves across apex into colloid
- forms into thyroglobulin to form MIT and DIT
- T3 and T4 formed
- T3 and T4 moved back into follicle for storage along with thyroglobulin
MIT + DIT forms
T3
DIT + DIT forms
T4
what couples the reaction combining MIT and DIT?
thyroid peroxidase
thyroid hormones stored in cell until…
thyroglobulin is taken back up (taken together)
TSH moves what into the cell?
thyroglobulin
how are T3 and T4 released into the bloodstream?
proteolysis of thyroglobulin complex
cellular action of thyroid hormones
-target cells throughout entire body
-T3 and T4 bind to nuclear receptors w/in cell nucleus and regulate gene expression
-stimulate metabolic rate
how do thyroid hormones stimulate metabolic rate?
-increasing number & size of mitochondria
-increasing Na/K ATPase concentration
-increasing Na and K membrane permeability
what is unique about thyroid hormones?
bind w/in the nucleus
*most others bind in the cytoplasm
how are thyroid hormones regulated?
negative feedback loop
what happens if there is too much T3 or T4?
inhibits TRH (which in turn does not produce TSH)
OR
inhibits TSH
both stop production of T3 and T4
hyperthyroidism
high T3 and T4 levels
low TSH levels
increased metabolic rate
hypothyroidism
low T3 and T4 levels
high TSH levels
decreased metabolic rate
thyroid function tests used to detect
TSH levels
T4 levels (free and total)
T3 levels (free and total)
*primarily focus on free levels b/c that is what is available to move into cells
factors that affected thyroid function tests
-diurnal variation (should take tests at same time of day to avoid this)
-temperature
-medications (steroids, estrogens)
-acute illness or stress
steroids ____ thyroid secretions
inhibit
estrogens ____ thyroid secretions
increase
thyroid gland disorders have higher incidence in…
females
common symptoms of hyperthryoidism
*increase metabolic rate
-goiter
-general: excitation, tremor
-tachycardia
-weight loss
-intolerance to heat
oral manifestations of hyperthyroidism
-increased risk for caries & periodontal disease
-burning mouth syndrome
-enlargement of thyroid tissue
-maxillary and mandibular osteoporosis
-severe dry mouth
causes of hyperthyroidism
-Grave’s disease (autoimmune disorder)
-thyroiditis (recent infection); temporary
-medications
amiodarone
can cause hypo- and hyperthyroidism
has iodine in chemical structure –> can be uptaken by thyroid and influence thyroid hormone levels
Grave’s disease
autoimmune disorder where antibodies are produced that stimulate TSH
*not regulated by negative feedback loop so will cause increased levels of T3 and T4
hyperthyroidism treatment
-antithyroid drugs (inhibits thyroid peroxidase)
-iodine (uses negative feedback loop)
-radioiodine (produces hypothyroidism)
-surgery (removal of thyroid gland)
dental complications of radioiodine therapy
-dry mouth
-increased risk of caries
-permanent taste loss
-increase salivary gland malignancies
common symptoms of hypothyroidism
*reduces metabolic rate
-goiter
-general: fatigue, lethargy
-bradycardia
-weight gain
-intolerance to cold
oral manifestations of hypothyroidism
-salivary gland enlargement
-macroglossia (enlarged tongue)
-glossitis (painful tongue)
-dysgeusia (altered taste)
-thick lips
-mouth breathing
-delayed bone reabsorption
causes of hypothyroidism
-Hashimoto’s disease (autoimmune disorder)
-pituitary or hypothalamic disease
-medications
-thyroid removal
Hashimoto’s disease
autoimmune disorder
T-cell mediated disorder where immune system attacks and destroys the thyroid
*thyroid peroxidase antibodies & thyroglobulin antibodies detected in blood
hypothyroidism treatment
thyroid replacement
-levothyroxine (synthetic T4)
-liothyronine (synthetic T3)
-armour thyroid (combination of synthetic T3 and T4)
thyroid cancer
-2-4x more likely in women
-develops around 45-50 years old
-growth of cells w/in the thyroid
-may involve esophagus, trachea, or laryngeal nerve
symptoms include
-asymptomatic
-hoarse voice
-difficulty breathing or swallowing
what type of hormones are made by the cortex of adrenal glands?
-mineralocorticoids
-glucocorticoids
-adrenal androgens
what type of hormone is made by the medulla?
catecholamines
zona glomerulosa
-outermost layer of adrenal cortex
-synthesizes aldosterone
zona fasciculata
-middle layer of adrenal cortex
-synthesizes cortisol
zona reticularis
-deepest layer of adrenela cortex
-synthesizes dehydroepiandrosterone (DHEA) and testosterone
medulla
-core part of adrenal gland
-synthesizes epinephrine and norepinephrine
adrenal hormone synthesis
- cholesterol absorbed from diet or synthesis in the body
- cholesterol hydrolysis
- cholesterol converted to pregnenolone which is moved into mitochondria
- pregnenolone then moved to ER and converted to progesterone
- progesterone converted to other steroids
how are adrenal hormones regulated?
negative feedback loop
-ACTH action inhibited
glucocorticoids action within the cell
- cortisol crosses and binds to receptors in cytoplasm
- Hsp releases allowing hormones to move to nucleus
- bind to glucocorticoid response element (GRE) w/in DNA
- can increase or decrease gene transcription
glucocorticoids (cortisol) hormone actions
*metabolic in the liver
*catabolic in muscles and fat
-increase blood glucose
-maintain BP
-mood changes
-increased glomerular flow
-anti-inflammatory
mineralocorticoid (aldosterone) hormone actions
sodium & water retention
androgens (DHEA and testosterone) hormone action
limited effects
catecholamines (epinephrine and norepinephrine) hormone actions
maintain BP and heart rate
Cushing’s disease
-excess cortisol
-increased production of: androgens, mineralocorticoids, and glucocorticoids
Addison’s disease
-cortisol deficiency
-decreased production of: androgens, mineralocorticoids, and glucocorticoids
does Cushing’s or Addison’s disease have more effects?
Cushing’s disease
general clinical manifestations of Cushing’s disease
-weight gain
-myopathy
general clinical manifestations of Addison’s disease
-weight loss
-weakness
oral manifestations of Cushing’s disease
delayed healing
oral manifestations of Addison’s disease
hyperpigmentation of oral mucosa
measuring adrenal gland function
-cortisol levels
-ACTH stimulation test
-adrenal gland imaging
treatment of Cushing’s disease
-surgical removal of adrenal glands
-removal of excess glucocorticoid
treatment of Addison’s disease
steroid replacement
