thyroid and pituitary Flashcards
thyroid makes more t3 or t4?
t4
t3 or t4 bioactive?
t3
TSH level in hyperthyroidism
low
what vitamin interferes w/ thyroid testing?
biotin
1 cause of correctable intellectual disability
iodine deficiency
amiodarone, lithium,, tyrosine kinase inhibitors (sunitinib, sorafenib; 50%) can all cause ____
hypothyroidism
1st line for hypothyroidism
levothyroxine
counseing for levothyroxine
Take on empty stomach w/ water only
* 30min-1 hour before breakfast
* Take at night
* Careful w/ soy products – can decrease absorption of levothyroxine
DI: Aluminum containing antacids
o PPIs
o Bile acid sequestrants
o Iron supplements
o Calcium supplements
o Ciprofloxacin
o Estrogens (OCPs)
o Grapefruit
Drugs impairing levothyroxine absorption, separate administrations times by 4 hrs
how long to monitor TSH after initial dose or dose change of levothyroxine
6 wks. then 6-12 months
levothyroxine dosing for in pregnancy / OCPs
dose needs to be higher. separate prenatal vitamin by 3 hrs
dosing of levothyroxine
1.6mcg/kg
AEs of excessive dosing: Cardiac: heart failure, angina, MI, tachycardia, palpitations, Afib
§ Skeletal: reduced bone density
* Increased risk of fracture; similar profile to osteoporosis
§ GI disturbances: abdominal cramps, diarrhea
levothyroxine
indication: thioureas / thioamides
hyperthyroidism
class: Propylthiouracil (PTU), Methimazole (Tapazole)
thioureas / thioamides
MOA: inhibit enzyme thyroid peroxidase
* Prevents conversion of iodide to iodine à functional T4/T3 cannot be made
thioureas
thiourea that blocks conversion of t4/t3 in periphery
PTU
thiourea used in 1st trimester of pregnancy
PTU
AEs: Higher risk of teratogenicity; aplasia cutis
methimazole
AEs: Arthralgias, lupus-like symptoms
* Fever
* Rash
* Transient leukopenia
* Agranulocytosis (rare, but serious)
* Hepatotoxicity w/ both, but more severe w/ PTU
thioureas
monitoring if on thioureas
baseline CBC, LFTs
add __ to thioureas
BB
1st line BB for hyperthyroidism
propranolol
MOA: block many hyperthyroidism manifestations mediated by B adrenergic receptors
* Some T4 to T3 conversion is blocked
BB
CI for radiactive iodine
pregnancy / breastfeeding
counseling for radioactive iodine
maintain 6ft distance and avoid public transport for several days. don’t get pregnant for 6 months. no intercourse for few days
class:
SSKI – saturated solution of potassium iodide
§ Lugol’s solution – potassium iodine-iodide
iodide solutions
MOA: acutely block thyroid hormone release, inhibit thyroid biosynthesis, decreases size and
vascularity of thyroid glands
iodide solutions
iodide solutions before or after radiactive iodine albation
after only
iodide solutions as monotherapy?
no
AEs:
* Rash, metallic taste, mucous membranes ulcerations, fever
iodide solutions
1st line for thyroid storm
PTU (preferred) or methimazole
give ___ 2nd in thyroid storm
Iodide solution: SSKI or Lugol’s solution
Most abundant hormone produced by anterior pituitary lobe
GH
first test to do if suspected acromegaly
serum IGF-1. will be elevated
1st line treatment for acromegaly
surgery
1st line med for acromegaly
Somatostatin (GHIH) analogs – first line medication
o Octreotide (sandostatin), Lanreotide, Pasireotide
MOA: mimic endogenous somatostatin and bind to somatostatin receptors in pituitary
* Inhibits GH and subsequently IGF-1
Somatostatin (GHIH) analogs
best efficacy somatostatin
pasireotide
AEs:
§ GI disturbances
§ Biliary sludge
§ Asymptomatic gallstones
§ May alter balance of counterregulatory hormones (glucagon, insulin, GH) à hyper or
hypoglycemia
§ Higher incidence of hyperglycemia w/ DM
§ May suppress pituitary release of TSH à hypothyroidism
somatostatin analogs
monitoring for somatostatin analogs
thyroid function and glucose
drug cautions w/ somatostatin analogs
Caution with insulin, oral hypoglycemic agents, BB, CCB à sinus bradycardia, conduction
abnormalities, arrhythmias
class: Pegvisomant (Somavert)
GH receptor antagonist
Most effective agent in normalizing IFG-1 concentration in acromegaly
Pegvisomant (Somavert)
main AE of Pegvisomant (Somavert)
hepatoxicity
Pegvisomant (Somavert) is a great option for acromegaly pts w/ _____
DM
class: Cabergoline, Bromocriptine
dopamine agonists
monitoring while on dopamine agonists
echos
these meds can cause….
Somatostatin analogs, GnRH agonists (ex: octreotide), methoxamine, phentolamine, isoproterenol,
glucocorticoids, methylphenidate, amphetamine derivatives
GH deficiency
main pharm tx for GH deficiency
Recombinant Human Growth Hormone (somatotropin)
time of day to administer Recombinant Human Growth Hormone (somatotropin)
evening
AEs:
§ Edema, arthralgia, myalgia, carpal tunnel syndrome, benign increases in ICP (HA, vision
changes, AMS)
* Adults > children
Recombinant Human Growth Hormone (somatotropin)
Recombinant Human Growth Hormone (somatotropin) CIs
Patients w/ active malignancy and obese/respiratory compromise in a child w/ Prader-Willi
syndrome
prolactin is inhibited by ____
dopamine
most common endocrine disorder of hypothalamic-pituitary-axis
hyperprolactinemia
Any medications that antagonize dopamine or stimulate prolactin can induce hyperprolactinemia
such as ______
o Risperidone (major!), metoclopramide, antidepressants, cimetidine, methyldopa, verapamil
1st line med for hyperprolactinemia
dopamine agonists (cabergoline)
Women who become pregnant while taking a dopamine agonist should _____
discontinue treatment to
minimize fetal exposure
