Week 4 - Endocrine Drugs Flashcards
Primary tx for hypothyroidism is
hormone replacement
In primary hypothyroidism what is used to monitor tx
TSH concentration
in hypothyroidism, Free T4 is what type of indicator??
what do we expect it to be normal or abnormal?
normal range when TSH is inhibited
Measurement of free T4 is warranted in
secondary hypothyroidism when TSH release is impaired
TSH release is impaired in
secondary hypothyroidism
T4 is the prohormone to?
T3
Goal of therapy for hypothyroidism: (4)
- Correction of hypothyroidism to euthyroid
- Reduction of symptoms
- Reduction in goiter size
- Prevention of cancer recurrence
when you see goiters, what are some of our concerns?
- difficult airway
- pressure on airway
- tracheal displacement/deviation
In PRIMARY hypothyroidism what do we see/find?
- Increase [plasma] of TSH
- Primary defect is OF thyroid
- Ant. Pituitary attempts to stimulate hormonal output by releasing TSH (hence the elevated TSH level)
In SECONDARY hypothyroidism what do we see/find?
Defect is at:
- hypothalamus OR the
- Ant. Pituitary
–> Low concentrations of both TSH and thyroid hormones circulating in plasma
Tx of choice for primary hypothyroidism:
T4: Levothyroxine (synthetic)
T4 half life is
7-10days
**allows for missing a dose for several days w/o adverse consequences.
IV(parenteral) T4 can be administered at what percent of patients oral dose?
80%
example: take 100mcg/day == 80mcg/day IV
An isomer of T3; supplemental T3 is:
Liothyronine
Liothyronine is ___ to ___ times as potent as levothyroxine.
- 5 to 3 times as potent
- rapid onset; short DOA
Is T3/Liothyronine used for long term replacement?
no - b/c of short doa and rapid onset
How do we tx HYPERthyroidism?
- Anti-thyroid meds
- radioiodine
- and/or surgery
***TSH levels useful for determining diagnosis of hyperthyroidism but not for
degree of severity
Measuring free T3 and T4 is necessary to assess
in hyperthyroidism
the efficacy of treatment
Once steady state achieved, what level can be used to assess the efficacy of therapy
TSH
Compounds that interfere with synthesis of thyroid hormones or reduce amount of thyroid tissue:
- Thionamides
- Inhibitors of iodide transport mechanism
- Iodide
- Radioactive iodine
‘TIIR
examples of Thionamides:
Methinmazole
Propylthiouracil
Carbimazole
(MOA) Thionamides: exert immunosuppressive effect via a reduction in concentrations of
anti-thyrotropin-receptor antibodies
In addition to blocking hormone synthesis, Propylthiouracil also inhibits
the peripheral deiodination (removal of iodine) of T4 and T3.
anti-thyroid drugs are useful in tx before
elective surgery
**don’t want to have a T.Storm during surgery
thionamides levels peak:
1-2 hrs after ingestion
are thionamides available in parenteral form?
no
Methimazole half life is:
4-6 hrs and dosed every day
Half life of propylthiouracil is:
75 mins!!!
dosed several times a day
*poor compliance
Minor side effects of thionamide therapy are observed in ~ 5% of pts:
- Urticarial
- Macular skin rash
- Arthralgias
- GI discomfort
- **Granulocytopenia and agranulocytosis are serious but rare; most likely to occur in first 3 months of anti-thyroid drug therapy
**Granulocytopenia and agranulocytosis are serious but rare. if to occur, when would they?
most likely to occur in first 3 months of anti-thyroid drug therapy
** what may be the earliest sign of development of agranulocytosis?
Pharyngitis or fever may be
Recovery is likely if the anti-thyroid drug is d/c’ed at the first signs.
propylthiouracil has reported toxicity of what?
hepatic
**which anti-thyroid crosses the placenta AND appears in breast milk?
methimazole
**Which anti-thyroid has limited placental crossing and is the preferred drug for use in pregnancy?
Propylthiouracil
the oldest available therapy for hyperthyroidism is:
iodide
*** Most important clinical effect of high doses of iodide is:
is inhibition of release of thyroid hormone.
….May reflect ability of iodide to antagonize the ability of TSH and cyclic adenosine monophosphate to stimulate hormone release
Iodide useful in tx before elective
thyroidectomy.
Combination of oral potassium iodide and propranolol is a recommended approach.
Combination of oral potassium iodide and propranolol is a recommended approach for :
tx before elective thyroidectomy.
Allergic reactions to iodide:
- angioedema and
- laryngeal edema:
- life threatening.
therapy of choice for Grave’s hyperthyroidism
Radioiodine
** Radioactive iodide is administered after ….
euthyroidism is achieved via thionamides
____ (form of radioactive iodide) is most administered and is rapidly and efficiently trapped by thyroid gland cells and the subsequent emission of destructive Beta rays act almost exclusively on these cells with little of no surround damage
131-I
131-I can destroy thyroid gland in how many weeks?
6-18 weeks