Thyroid Disorders and Parathyroid Disorders Flashcards
What is a goiter?
Enlargement of the thyroid gland
What is Grave’s disease?
Autoimmune disorder that results in hyperthyroidism during the early phase and can progress to hypothyroidism if there is destruction of the gland in later phases
What is thyroglobulin?
A protein synthesized in the thyroid gland; its tyrosine residues are used to synthesize thyroid hormones
What is TSH?
The anterior pituitary hormone that regulates thyroid gland growth, uptake of iodine and synthesis of thyroid hormone
What is a thyroid storm?
Severe thyrotoxicosis
What is thyrotoxicosis?
Medical syndrome caused by an excess of thyroid hormone
If a pt comes in with a goiter. do they have hyper or hypo thyroidism?
we DONT know yet, need to do more testing to determine
What is thyroxine-binding globulin (TBG)?
Protein synthesized in the liver that transports thyroid hormone in the blood
Role of thyroid in child? adult?
normal growth/development
maintain metabolic stability
TSH is under the control of…
the hypothalamic hormone thyrotropin-releasing hormone
What hormones are release by the thyroid?
Thyroxine, Triiodothyronine
What are the 2 ways that the thyroid func. is regulated?
TSH secreted by the anterior pituitary > secretion of TSH under negative feedback
Extrathyroidal deiodination of T4 to T3
What regulates conversion of T4 to T3?
nutrition nonthyroidal hormones ambient temperatures drugs illness
What is required for thyroid hormone synthesis?
Iodine
Thyroglobulin
Which thyroid hormone is predominantly secreted from the thyroid gland?
T4
T4 is then converted to T3
they are highly protein bound, only the unbound is active
Where are thyroid hormone receptors found?
in the most hormone responsive tissues: pituitary, liver, kidney, heart, skeletal muscle, etc.
(# of receptors may be altered to preserve body homeostasis)
Besides T3 and T4, the thyroid also releases…
calcitonin
Key features of thyrotoxicosis?
warm/moist skin, sweating, heat intolerance, tachycardia, dyspnea, increased appetite, nervousness, weight loss, exophthalmos
Key features of hypothyroidism?
pale/cool/puffy skin, sensation of being cold, bradycardia, reduced appetite, lethargy weight gain
What are some causes for hypothyroidism?
hashimoto’s, drug induced, dyshormonogenesis, radiation, congenital, secondary (TSH deficit)
Labs of pts with hypothyroidism?
primary: elevated TSH, decreased serum free T4
secondary: assess only free T4 –> free T4 and T3 low , antithyroid peroxidase abs in autoimmune thyroiditis
TSH of … is concerning for hypothyroidism. TSH of ….is concerning for subclinical hypothyroidism
10
> 4.5
When do you need to carefully monitor hypothyroidism lab studies?
during pregnancy
may need to increased dosage
In hyperthyroidism TSH is?
In hypothyroidism?
low
high
Besides hypothyroid, what can cause low serum T4 and T3?
LOTS of drugs
i.e. Salicylates, NSAIDS, Octreotide
Drug of choice for tx of hypothyroidism?
Levothyroxine (synthetic T4)
Half life of levothyroxine? What is unique about its dosing?
7 days (so can dose daily)
color represents a tablet strength
Which levothyroxine dose does not contain any dye?
50 mcg
When do you change a dose of levothyroxine, when do you recheck a TSH?
in 4-6 weeks because it has reached steady state after 4-5 half lives
Relationship btwn T4 and concentration and TSH…
is not linear, small change in T4 can lead to big change in TSH
What can impair absorption of Levothyroxine (T4)?
food, mucosal diseases, GI tract
-needs to be taken on any empty stomach with water only
What drugs can increase T4 clearance?
rifampin
carbamazepine
possibly phenytoin
What other drugs can be used for the tx of hypothyroidism?
Lipthyronine
Liotix
Thyroid USP
Why do people like taking T3 (Liothyronine)?
has a short half life and gives them a burst of energy
BUT gives more than the body would have normally
Content of Thyroid USP (Armour Thyroid)?
desiccated pork thyroid gland
High T3: T4 ratio
not really recommended
dose requirement for thyroid replacement may be better estimated by….rather than on actual body weight
ideal body weight
Average thyroid replacement dose requirement
1.7mcg/kg/day
once they reach steady state
Levothyroxine dose for Young patients with long-standing disease and patients over age 45 without known cardiac disease?
start on 50 mcg Levothyroxine daily
then increase to 100 mcg daily after 1 months
How should levothyroxine dose be adjusted in older pts?
initial daily dose for older patients or those with known cardiac disease is 25 mcg per day
then titrate upward in increments of 25 mcg at monthly intervals to prevent stress on the cardiovascular system
What can accelerate thyroxine disposal?
nephritic syndrome
other severe systemic illness
several antiseizure meds and Rifampin
Levothyroxine dosage in pregnant women?
what about for postmenopausal women on hormone replacement therapy?
Pregnancy increases the thyroxine dose requirement for 75% of women
increases dose need in 85% of women
What drugs can be effected by hypothyroidism?
Digoxin > higher serum levels
might decrease sensitivity to Warfarin, restoration of euthyroidism can increase the warfarin dose requirement
Excessive doses of thyroid hormone may lead to…
heart failure
angina pectoris
MI
Which Levothyroxine tablet is the least allergenic?
0.05 mg (50 mg)
white tablet - no dye
Hyperremodeling of cortical and trabecular bone due to hyperthyroidism, may lead to…
reduced bone density and may increase the risk of fracture
Besides hypothyroid, TSH-suppressive Levothyroxine therapy may also be used for…
nodule thyroid disease and diffuse goiter
hx of thyroid irradiation
thyroid CA
When should Levothyroxine be taken?
on any empty stomach, ideally an hour before breakfast
What meds may interfere with Levothyroxine absorption? When should they be taken?
ferrous sulfate
PPIs
calcium carbonate
bile acid resins
4 hrs after levothyroxine dose
Sxs of hyperthyrodisim?
Cardinal sign is loss of weight concurrent with an increased appetite
Nervousness Anxiety Palpitations Emotional lability Easy fatigability Menstrual disturbances Heat intolerance
PE findings in hyperthyroidism?
findings specific to Graves’s disease?
Warm, smooth, moist skin
Unusually fine hair
exophthalmos
pretibial myxedema
What are the treatment options for hyperthyroidism??
antithyroid drugs
RAI
surg
Advantages of antithyroid drugs? disadvantages?
(+) noninvasive, low initial cost, low risk of permanent hypothyroidism
(-) low cure rate, ADEs, drug compliance
antithyroid drugs are considered first line for which pts?
children, adolescents, and in pregnancy
Examples of antithyroid drugs?
Thiourea drugs
- Propthyouracil (PTU)
- Methimazole (MMI)
MOA of PTU and Methimazole?
serve as preferential substrates for the iodinating intermediate of thyroid peroxidase and divert iodine away from potential iodination sites in TG
> inhibit coupling of monoiodotyrosine and diiodotyrosine to form T4 and T3
PTU and Methimazole are mostly absorbed where?
GI tract (80-95%)
actively concentrated in the thyroid gland
Dosing for PTU? Methimazole?
initial dose 300-600mg daily, divided in 3-4 doses
MMI: 30-60mg/day divided in 2-3 doses
After starting PTU or Methimazole, when is there usually improvement in sxs?
within 4-8 wks
changes in dose should be made on a monthly basis
ADEs of PTU and Methimazole?
agranulocytosis, rash, benign transient leukopenia, arthralgias & a lupus like syndrome, hepatoxicity
What is agranulocytosis?
serious adverse effects of thiourea drug therapy and is characterized by fever, malaise, gingivitis, oropharyngeal infection, and a granulocyte count less than 250/mm3
What drug for hyperthyroidism can be used during the first trimester of pregnancy? what about for the remainder of pregnancy?
PTU
MMI: risk of hepatotoxicity > risk of embryopathy
MOA of iodides in Graves’s disease?
acutely blocks thyroid hormone release
inhibits thyroid hormone biosynthesis by interfering with intrathyroidal iodine utilization
decreases size/vascularity of the gland
How long after staring Iodine therapy will pts have sxs improvement?
2-7 days
Caveat to Iodide therapy?
Despite the reduced release of T4 and T3, thyroid hormone synthesis continues at an accelerated rate, resulting in a gland rich in stored hormones
When used in addition to RAI, SSKI should be given…
3-7 days after RAI tx so that the RAI can concentrate in the thyroid
When should Potassium iodide be given when used preoperatively?
7-14 days preoperatively
ADEs of iodides?
Salivary gland swelling
“Iodism” > metallic taste, burning mouth/throat, sore teeth/gums, gynecomastia, GI upset
hypersensitivity rxn
When can be used for hyperthyroid sxs relief?
Adrenergic blockers: Propranolol
MOA of propranolol?
Blockage of beta adrenergic receptors
Indications for propranolol for hyperthyroidism?
usually adjunct to antithyroid drugs
primary therapy for thyrotoxicosis
Contraindications for propranolol?
decompensated HF, sinus brady, MOAI or TCA use, spontaneous hypoglycemia
How can BB effect pregnancy?
prolong gestation and labor during pregnancy
ADEs of Propranolol?
nausea, vomiting, anxiety, insomnia, light-headedness, bradycardia, and hematologic disturbances
Advantages to radioactive iodine? disadvantages?
(+) cure of hyperthyroidism, most cost effective
(-) permanent hypothyroidism almost inevitable, pregnancy most be deferred for 6-12 mos/no breast feeding, might worsen opthalmopathy, small risk of exacerbation of hyperthyroidism
RAI is the best treatment for…
toxic nodules and toxic multinodular goiter
Advantages of surg for hyperthyroidism? disadvantages?
fast & effective, especially in pts with large goiters
most invasive, potential comps (recurrent laryngeal n. damage, hypoparathyroidism), most costly, permanent hypothyroid
Potential tx for pregnant pts who are intolerant of antithyroid drugs?
surgery
Which drugs can be used in the management of thyroid storm?
PTU MMI Sodium Iodide Lugol's solution Saturated Solution of Potassium Iodide Propranolol Dexamethasone, Prednisone, Methylprednisolone, Hydrocortisone
TSH receptor-stimulating antibody or thyroid-stimulating immunoglobulin (TSI) may be elevated in?
Graves’s disease
hyperthyroidism
Presentation of hypoparathyroidism?
usually asxs
Acute: mild-severe tetany
Chronic: lethargy, anxiety/depression, urolithiasis, renal impairment, dementia, blurry vision from cataracts of keratoconjuctivitis
What systems are effected by hypoparathyroidism?
endocrine/metabolic
musculoskeletal
nervous
opthomalogic
renal
What is PTH involved in?
the control of serum ionized calcium levels
What happens where there is loss of PTH action?
hypocalcemia
hyperphosphatemia
hypercalciuria
What is crucial for PTH secretion and activation of the PTH receptor?
Mg
Tx of hypoparathyroidism?
- Maintain serum calcium in low-norm range 8-8.5
- oral calcium carbonate
- Calcitrol
- Maintain serum Mg in range
- Phosphate binders if high calcium phosphate product
- Thiazide diuretics + low salt diet
What alternative to calcium carbonate can be used in geriatric pts, those on PPI or those with constipation?
calcium citrate
Why are Thiazides and low salt diet recommended for pts with hypoparathyroidism?
to prevent hypercalciuria, nephrocalcinosis and nephrolithiasis
In pt with hypoparathyroidism, what should be monitored wkly during initial management?
Ca
Phosphate
Mg
Cr
Describe primary hyperparathyroidism
intrinsic parathyroid gland dysfunction resulting in excessive secretions of PTH with a lack of response to feedback inhibition by elevated calcium
Describe secondary hyperparathyroidism. Tertiary?
excessive secretion of PTH in response to hypocalcemia, which can be caused by vitamin D deficiency or renal failure
autonomous hyperfunction of the parathyroid gland in the setting of long-standing secondary HPT
High PTH (>3) suggests…
Low PTH (<3) suggests…
primary HPT
non-PTH mediated hypercalcemia
What is curative for primary HPT?
operative management
for those awaiting/unable to have surg:
-Bisphosphonates (Alendronate)
- Calcimimetics
- Selective estrogen receptor modulator therapy
- Hormone replacement (postmenopausal women who refuse surg)
Tx for secondary HPT?
Calcium replacement
Vitamin D analogues (paricalcitol and calcitriol)
Phosphorus-binding agents (sevelamer)
Calcimimetic (cinacalcet): activates calcium-sensing receptor in parathyroid gland thereby inhibiting PTH secretion
tx for tertiary HPT?
Medical treatment is not curative and generally not indicated
Minimum dietary requirement for iodine?
75-150mg/day
Thyroglobulin (Tg) levels are used primarily in____, can also be elevated in_____
Thyroid CA
Acute thyroiditis, Graves’s disease
You would most likely see elevated Antithyroid Microsomal ABs (Antithyroid peroxidase Abs) in?
Hashimoto’s disease
less common: graves
You would most likely see elevated Tg abs in?
Hashimoto’s disease
less common: graves (Helpful to predict if patient with Graves’ will eventually become hypothyroid without iatrogenic destruction of the gland)
TSH receptor abs (TrAB) can be?
stimulating, blocking or neutral
ex. TSI, TBII
Thyroid stimulating immoglobulins (TSI) are commonly seen in?
Graves
less common: Hashimoto’s
What test is used as the newborn screening for hypothyroidism?
total T4
What type of nodule is more likely to be CA?
cold (hypofunctioning)
