ICL 1.2: Thyroid Disorders and Pharmacology Flashcards
(68 cards)
1
Q
what are the actions of the thyroid hormones?
A
- increase Na/K ATPase activity
- increase oxygen consumption
- increase heat production
- drive brain maturation
- allow tissue growth
- increase free radical production
- increase beta adrenergic responses
2
Q
what condition does increased RSH, decreased free T4 indicate?
A
primary hypothyroidism
3
Q
what condition does increased TSH and normal free T4 indicate?
A
mild thyroid failure
aka sub-clinical hypothyroidism
4
Q
what condition does increased TSH and increased free T4/T3 indicate?
A
- thyroid hormone resistance
2. TSH secreting tumor
5
Q
what condition does decreased TSH and high free T4 or T3 indicate?
A
thyrotoxicosis
6
Q
what condition does decreased TSH and normal free T4 or T3 indicate?
A
subclinical hyperthyroidism
7
Q
what condition does decreased TSH, low free T4 and normal or low T3 indicate?
A
- central hypothyroidism
2. sick euthyroid
8
Q
what thyroid imagining techniques do you use?
A
- US
- I-131 uptake/scan
- Tc-99 scan
9
Q
what is thyroid US used for?
A
- assessing nodular disease
- aids in aspiration
- assessing vascular flow for cancer risk
10
Q
what is the I-131 uptake scan used for?
A
- differentiates causes of thyrotoxicosis
- determining treatment
Tc-99 scan is the same but with inferior resolution
11
Q
what are the etiologies of hypothyroidism?
A
- surgical
- post-ablative
- infiltrative disease
- autoimmune destruction
- inflammatory
- drugs: lithium, amiodarone, interferone
- hreditary/congenital
12
Q
what are the 3 clinical presentation of hypothyroidism?
A
- mild thyroid failure
- overt hypothyroidism
- myxedema coma
13
Q
what are the signs and symtpoms of hypothyroidism?
A
- fatigue
- cognitive slowing
- weight gain
- cold tolerance
- hoarseness
- dry skin and hair
- brady cardia
- pericardial effusion
14
Q
what are he lab findings for hypothyroidism?
A
- TSH elevated in primary diseases; low in central disease
- free T4 is normal or low
- T3 is often normal until disease is advanced
- elevated cholesterol
- hyponatremia
- elevated CK
- hypoglycemia in advanced cases
15
Q
how do you treat hypothyroidism?
A
levothyroxine is DOC
80% of orally ingested dose is absorbed mostly in the proximal and mid small bowel so should be taken on empty stomach
peak levels occur 2-4 hours after ingestion; it’s protein bound
25-300 mcg daily
16
Q
what drug interactions do you need to keep in mind when treating hypothyroidism?
A
- dose requirements decrease with age
- dose requirements increase with pregnancy or any cause of increased circulating estrogen
- phenytoin increases thyroid hormone metabolism
- cholesterol binding resins like calcium and soy can decrease absorption
- T1/2 is 7 days for T4 and 24 hours for T3
17
Q
how do you assess if treatment of hypothyroidism is working?
A
adequacy of treatment tis assessed by measurement of TSH
TSH does not stabilize for 4-5 weeks after a dose change of T4
18
Q
what are the considerations you give when treating hypothyroidism in elderly and pregnant patiuets?
A
elderly patients and those with coronary artery disease: start with low dose 12.5-25 mcg daily
pregnancy: requirements may increase as early as 5 weeks gestation; inadequate maternal replacement may result in reduction in fetal IQ
19
Q
what is a myxedema coma?
A
hypothyroidism with respiratory insufficiency, hypothermia and mental status changes
an acute medical emergency
often precipitated by infection, CVA, MI and prolonged omission of levothyroxine
mortality is realted to the precipitating cause
20
Q
how do you treat myxedema coma?
A
- ventilatory support
- fluid therapy
- T4 replacement given IV; initial loading dose 300 mcg followed by 50 mcg daily
- give hydrocortisone 100 mg every 8 hours until adequacy of adrenal cortical function is established
TREAT THE PRECIPITATING CAUSE
21
Q
when is levothyroxine used for suppressive therapy?
A
- thyroid nodules
20% effective but no longer recommended
- thyroid cancer
22
Q
what are the etiologies of thyrotoxicosis?
A
aka high I-131 uptake in:
1. graves disease
- TMNG
- toxic adenoma
- TSH secreting tumor
- thyroid hormone resistance syndrome
- struma ovaria
- metastatic follicular cancer (rare)
23
Q
what are the 3 clinical syndromes of thyrotoxicosis?
A
- subclinical hyperthyroidism
- overt thyrotoxicosis
- thyroid storm
24
Q
what are the signs of thyrotoxicosis?
A
- tremor
- palpitations, tachycardia, wide pulse pressure
- hyperdefecation
- heat intolerance, increased sweating
- weight loss
- muscle weakness
- irritability, agitation
- insomnia
25
what are the lab findings of thyrotoxicosis?
1. low TSH; usually completely suppressed
2. T4 is normal to elevated
3. T3 is normal to elevated; in a critically ill patient a high normal or frankly elevated T3 is highly indicative of thyrotoxicosis
4. low cholesterol
5. hypercalcemia
6. hyperglycemia
26
what is Graves disease?
1. thyrotoxic symptoms
2. goiter +/- bruit
3. extra-thyroidal anifestations like oculopathy or dermopathy
4. more common in women
5. family history of other autoimmune glandular disorders
27
how do you treat Grave's disease?
1. antithyroid drugs: PTU or methimazole
2. radioactive iodine
3. surgery: subtotal thyroidectomy
4. B-blockers: propranolol
28
which drugs are antithyroid drugs?
thiocarbamides: PTU, methimazole
they inhibit intrathyroidal peroxidase
they do not affect iodine trapping or release of stored thyroid hormone
PTU inhibits conversion of T4 to T3; propranolol also does that
remission rates are 30-60% ):
29
what is the DOC for Graves in pregnancy?
PTU
30
what are the side effects of antithyroid drugs?
1. rash
2. agranulocytosis
3. toxic hepatitis
4. lupus like syndrome
5. arthralgia
6. fever
31
what is the DOC for Grave's in nonpregnant adults?
I-131
24 hr uptake prior to dosing and discontinue antithyroid drugs 10-14 days prior because recent iodine exposure interferes with I-131
may flare in hyperthyroid symptoms 1 week after therapy which is indicative of radiation thyroiditis
effects may not be apparent before 6 weeks
32
how effective is I-131 treatment for Graves?
70-80% tarted effectively with 1 dose at 1 year
permanent hypothyroidism is an expected outcome of I-131 treatment
no increased risk of malignancy in treated patients or ftal anomalies in offspring of women previously treated
women should defer pregnancy for 6 months after therapy though
33
when is I-131 treatment contraindicated?
there is increased progression of oculopathy if it was moderate to severe
so if they have pretty bad oculopathy just refer them to surgery; don't treat with radioactive iodine
34
why are B-blockers used for hyperthyroidism?
they're used as adjuvant therapy to control symptoms like arrhythmias and tachycardia
propranolol is what's used because it inhibits T4 to T3 conversion
35
what are the requirements for a subtotal thyroidectomy?
pretreatment with antithyroid drugs and B-blockers
90% effective
can be used in pregnancy during 2nd trimester
36
what are the complications of a subtotal thyroidectomy?
1. recurrent laryngeal nerve injury
2. hypoparathyroidism
3. permanent hypothyroidism
4. thyroid storm
37
how do you treat toxic nodular thyroid disease?
control symptoms with B-blcokers and antithyroid drug therapy but you will not see permanent remission with this therapy
I-131 therapy can be used if gland size and low I-131 uptake are not prohibitive
surgery is effective but is limited but he underlying health of the patient
patients often older and may present with apathetic thyrotoxicosis
38
what are the causes of thyrotoxicosis?
thyrotoxicosis is when the uptake scan shows hyperthyroid symptoms with low I-131 uptake and this is seen in:
1. thyroiditis (Hashimoto, subacute, postpartum)
2. iodine induced (amiodarone, iodinated contrast)
3. ingestion of thyroid hormone
39
how do you treat subacute thyroiditis?
self limited problem that requires symptomatic therapy only
so give them B-blockers for tachycardia and anti-inflammatory agents for thyroid pain; occasionally give prednisone to control pain
40
how do you differentiate subacute thyroiditis from ingestion of thyroid hormone?
thyroglobulin levels
thyroglobulin will be low if they patient is taking thyroid hormones
thyroglobulin will be detectable with thyroiditis
41
what is a thyroid storm?
life threatening medical emergency where patients present with thyrotoxicosis, fever and mental status changes
42
how do you treat thyroid storm?
1. supportive measures like sedation, rehydration, oxygen, cooling and treatment of the precipitating cause
2. propranolol 6-80 mg every 6 hrs
3. hydrocortisone 100 mg IV every 8 hrs
4. PTU 100-200 mg every 4-6 hrs
5. iopanoic acid 1 g every 8 hrs after initiation of PTU
43
how common is thyroid cancer?
it's the most common endocrine malignancy
35,000 new cases every year and more common in females; 5th most common in women
2,000 deaths per year; 6.6% overall mortality rate
4-17% of all thyroid nodules are malignant and incidence increases with age
44
what is the pathology of thyroid cancer?
80% from follicular epithelial cells while less than 20% from parafollicular cells, metastatic or lymphoma
45
what are the follicular vs. papillary subtypes of thyroid cancer?
FOLLICULAR
1. papillary
2. follicular
3. anaplastic
PAPILLARY
1. follicular variant
2. tall cell
3. trabecular cell
4. columnar cell
5. clear cell
6. solid variant
46
how common is papillary thyroid cancer?
60-70% of thyroid cancers
F:M 2.5:1
47
what is the prognosis of papillary thyroid canceR?
best prognosis if less than 4 cm, noninvasive and patient is under 45 years old
10 year survival is 90-95%
local LN mets are associated with increased recurrence
encapsulated papule is more favorable
TSH dependent so suppress TSH during treatment
48
how common if follicular thyroid cancer?
10-20% of thyroid cancers
F:M 3:1
49
what is the prognosis for follicular thyroid cancer?
encapsulated with minimal invasion and under 45 years old is an excellent prognosis \
10 year survival for minimally invasive is 86% but only 44% with highly invasive
hematogenous spread so there's increased malignant potential over time
secreted TG; rarely secreted T3
50
what are the variants of follicular cancer?
1. Hurthle cell
| 2. insular variant
51
how common is anaplastic thyroid cancer?
less than 10% of thyroid cancers
F:M 1.2:1
it's basically the undifferentiated form of papillary thyroid cancer
usually seen in older patients
52
what is the prognosis for anaplastic thyroid cancer?
highly malignant; 6-12 month survival
surgery/radiation is only palliative
may be difficult to differentiate from lymphoma or renal cell cancer metastatic to the thyroid since it's undifferentiated
53
how common is medullary thyroid cancer?
5%
F:M 1:1
it's a neuroendocrine origin
54
wha tis the prognosis for medullary thyroid cancer?
more aggressive than follicular cell but less than anaplastic
usually multifocal presentation with local and distant metastasis, even with small primary tumors
55
what are the biomarkers for medullary thyroid cancer?
1. calcitonin
2. CEA
3. chromogranin
56
can you screen for medullary thyroid cancer?
limited usefulness of calcitonin as a screening tool in thyroid nodules
can do RET screening though and it's associated with FMTC, MEN2a and MEN2b syndromes
57
what are the paraneoplastic syndromes associated with medullary thyroid cancer?
1. flushing
2. diarrhea
3. Cushings syndrome
58
what are the symptoms of MEN1 syndrome?
3Ps:
1. pituitary adenoma
2. parathyroid hyperplasia
3. pancreatic tumors
due to MEN1 mutation on chromosome 11
59
what is the clinical presentation of MEN2a?
1. medullary carcinoma of the thyroid
2. pheochromocytoma
3. hyperparathyroidism
RET mutation
60
what is the clinical presentation of MEN2b?
1. medullary carcinoma of the thyroid
2. pheochromocytoma
3. mucosal neuromas
4. Marfanoid body habits
RET mutation
61
how do you diagnose thyroid canceR?
palpable mass, incidental finding, genetic screening or cervical adenopathy
they usually have normal thyroid function studies
factors suggesting malignancy: rapid growth, compressive symptoms, hoarseness, stridor, dysphagia, extremes of age, male sex, radiation, exposure, hard fixed mass, adenopathy, vocal cord paralysis
radiation and family history are the strongest factors!
62
what are the fine needle aspiration results of papillary thyroid cancer?
large pale nuclei
prominent nucleoli
increased number of nucleoli
psammoma bodies
63
what are the fine needle aspiration results of follicular thyroid cancer?
cannot differentiate adenoma from carcinoma of FNA
so you can't differentiate malignant vs. benign without surgery and biopsy
64
which US findings suggest benign thyroid lesions?
1. hyperechoic lesions
2. halo effect
3. thin walled cyst
4. egg shell calcifications
65
which US findings suggest malignant thyroid lesions?
1. hypoechoic
2. thick walled cyst
3. intralesional calcification
4. large size
5. lymphadenopathy
6. LN size over 1 cm, spherical, loss of fatty hilum
however, you can't differentiate bening vs. malignant on us, you have to do FNA or biopsy; no US criteria reliably excludes malignancy!!!!
66
what srugery do you do for thyroid cancer?
1. total thyroidectomy is preferred for large papillary and follicular type cancers
2. lobectomy is sufficient for incidentally discovered microscopic papillary cancers
3. surgery for medullary cancer should include total thyroidectomy, bilateral central node dissection and ipsilateral modified radical neck dissection
total thyroidectomyvs. lobectomy lower reucrrence risk, prevention of recurrence in contralateral lobe, use of TG as a tumor marker after I-131 for total thyroidectomy, not a lobectomy because they'll still have TG being produced by normal tissue
67
what is the goal of thyroid hormone suppressive therapy in thyroid cancer patients?
complete TSH suppression in high risk patients
you've made them hyperthyroid so you have to be careful to watch for arrhythmias and bone loss
68
how do you follow up for thyroid cancer after treatment?
long term follow up due to risk of late recurrent
if I-131 is not give, do exam, TG, US, CXR, CT, MRI
TG should be less than 5 ng/dl in a patient with a remnant and they're off suppressive therapy so if they got a total thyroidectomy but you didn't do I-131 then it's fine if they're TG is around 5 since there's tissue left behind; if they did the thyroidectomy and I-131 then the TG should be undetectable
IS every 6 months for 2 years to check for lymph node metastasis and do a stimulated TG twice, two years apart and then measure the baseline TG at least yearly after that
if there's no uptake in a TG positive patient after an iodine dose, do a CT or PET scan
