Ch7: Thyroid Flashcards
what is T4
thyroxine
what is T3
triiodothyronine
what is the function of T3 and T4
these hormones act as cellular energy release catalysts and influence the function and health of every cell in the body
most common thyroid disorder encountered in primary care
hypothyroidism
MOMS SO TIRED mnemonic for hypothyroidism presentation
Memory loss Obesity Menorrhagia Slowness Skin/hair dry Onset gradual Tiredness Intolerance to cold Raised BP Energy levels fall Depression/delayed relaxation phase of all reflexes (especially patellar, Achilles)
what is the natural history of weight gain with hypothyroidism?
modest weight gain of <10lbs that is mostly fluid, will pee off this fluid when adequately treated
DTRs with hypothryoidism
delayed relaxation of DTRs - slow arc out and an even slower arc back
“hung up patellar reflex”
most noticeable in patellar and achilles DTRs
most common cause of hypothyroidism in the USA
chronic autoimmune hypothyroidism
aka Hashimotos thyroiditis
classic patient characteristics of someone with Hashimotos thyroiditis
> 50yo
female
causes of hypothyroidism
- autoimmune (Hashimotos)
- post-radioactive iodine treatment (e.g., after Graves dx)
- select medications (Lithium, amiodarone, interferon)
medications that can cause HYPOTHYROIDISM
- lithium (up to 1/3)
- amiodarone
- interferon
SWEATING mnemonic for hyperthyroidism
Sweating Weight loss Emotional lability Appetite increased but losing weight Tremor/tachycardia Intolerance of heat/irregular menstruation/irritability Nervousness Goiter, GI problems (diarrhea)
what is a goiter
descriptor for thyroid enlargement
most common cause of hyperthyroidism
Grave’s disease (autoimmune)
cluster of autoimmune conditions to keep on your radar if someone has autoimmune thyroid disease (5)
- rheumatoid arthritis
- lupus SLE
- vitiligo
- celiac dz
- T1DM
exophthalmos, suspect….
Grave’s hyperthyroidism
What is a toxic adenoma
benign (non-malignant) metabolically-active thyroid nodule that causes typical hyperthyroid symptoms but with palpable unilateral thyroid mass and NO exophthalmos
what is thyroiditis
inflammation of the thyroid
usually transient
can be caused by a viral infection, autoimmune condition, postpartum, drug-induced, etc.
typically has a milder symptom presentation with thyroid tenderness but without exophthalmos
medications that can cause hyperthyroidism (2)
- amiodarone
- interferon
hyper or hypothyroid: dry skin
hypothyroid
hyper or hypothyroid: fine tremor
hyperthyroid
hyper or hypothyroid: hypoactive DTRs (delayed relaxation)
hypothyroid
hyper or hypothyroid: mood changes
both
hyper or hypothyroid: menorrhagia
hypothyroid
hyper or hypothyroid: exophthalmos
hyperthyroid
normal range for TSH
0.4-4.0 mIU/L
what is the single most reliable test to diagnose all common forms of hypo and hyperthyroidism
TSH
thyroid-stimulating hormone
TSH is released by the…..
anterior pituitary
when TSH results are normal, can you rule out thyroid disease?
yes, very good sensitivity and specificity
normal range for free T4
10-27 pmol/L
normal range for thyroid peroxidase antibody (anti-TPO ab)
<35 IU/mL
second most helpful test for diagnosing hypo or hyperthyroidism
FREET4
not total
% of all T4 that is free
0.025%
majority of T4 is protein-bound
anti-TPO antibodies are used to detect….
Hashimoto’s thyroiditis
dx: TSH 84, free T4 3
high TSH
low free T4
untreated hypothyroidism
levothyroxine replacement doses for hypothyroidism
based on ideal body weight if obese, actual body weight if BMI WNL or underweight
- 1.6 mcg/kg/day in most adults
- 1.0 mcg/kg/day in elderly
check TSH after ____ weeks after starting levothyroxine for hypothyroidism
q6-8 weeks until euthyroid, then in 4-6 months, then yearly if stable
she says 8 WEEKS and any earlier can lead to errors in clinical decision-making
weight based dosing for levothyroxine: most adults
1.6 mcg/kg/day
ranges 50-200mcg for adults, typically
weight based dosing for levothyroxine: elderly
1.0 mcg/kg/day
T4/T3 combination medication?
Armour Thyroid
use is not recommended by the AACE due to variable pharmcokinetics
instructions for patient administration of levothyroxine
levothyroxine should be taken with plain water on an empty stomach, same time every day
should not be taken within 2 hours of cation such as calcium, iron, aluminum, magnesium , or others due to chelation effect with reduced drug absorption
dx: TSH 0.15, free T4 79
low TSH, high free T4
hyperthyroidism
treatments for hyperthyroidism
- non-cardioselective beta blockers (propanolol, nadolol) for counteracting tachycardia and tremor
- thyroid-ablative therapies (e.g., methimazole, PTU, RAI)
thyroid ablative therapy options in hyperthyroidism
- methimazole PO (Tapazole)
- PTU (Propylthiouracil)
- radioactive iodine
use the PO methimazole or PTU first to reduce thyroxine production to become euthyroid. Once euthyroid from antithyroid medications, use radioactive iodine with the goal of thyroid ablation with resulting hypothyroidism
usually treated in conjunction with endocrinology consult
do you want cardioselective or non-cardioselective beta blockers for hyperthyroidism?
non-cardioselective beta blockers
most commonly, propanolol
priority risk of methimazole and PTU
acute hepatic failure even in the absence of liver disease risk factors (e.g., alcohol use)
can happen to anyone
dx: TSH 8.9, total T4 15, TPO-ab 76
subclinical hypothyroidism
treatment for subclinical hypothyroidism?
recommend treatment if TSH >5 and presence of a goiter or TPO-antibodies, symptomatic, infertility/pregnant/trying to conceive
what range should you treat TSH to ideally with levothyroxine
0.5-2 uIU/mL
If you start levothyroxine, they come back in 6-8 weeks later and the TSH is still elevated (>4) – Dose titration?
increase levothyroxine dose by 12.5mcg to 25mcg
If you start levothyroxine, they come back in 6-8 weeks later and the TSH is now low (<0.5) – Dose titration?
decrease levothyroxine dose by 12.5 - 25mcg
follow-up interval for checking TSH after levothyroxine adjustments
q6-8 weeks until euthyroid, then 6 months, then annually
risk that any given thyroid nodule is malignant?
5%
role of a NP primary care provider in pt with a thyroid nodule
initiate evaluation, refer to specialist
what is a thyroid nodule
a palpable thyroid mass, not a term specific to a diagnosis. is clinically evident, typically >1cm in diameter
presentation of benign and malignant tends to be the same
5% risk of being malignant
findings most consistent with a MALIGNANT thyroid nodule?
- h/o head or neck irradiation
- size >4cm
- firmness, nontender on palpation
- relatively fixed position (nonmobile)
- persistent non-tender cervical lymphadenopathy
- dysphonia
- hemoptysis
pt presents with clinically evident thyroid nodule >1cm, next step?
labs: TSH
imaging: thyroid US
pt presents with clinically evident thyroid nodule >1cm. you order TSH and a thyroid US. lab results return low TSH. what is your next step?
refer for nuclear medicine thyroid scan to determine the nodule function and structure
will determine “hot” (releasing T4) aka toxic or non-toxic (not releasing excess T4) nodules
pt presents with clinically evident thyroid nodule >1cm. you order TSH and a thyroid US. lab results return low TSH. nuclear medicine thyroid scan reveals a “hot” nodule, diagnosed with toxic nodular goiter. what is the next step?
radioiodine ablation or surgery to remove it
pt presents with clinically evident thyroid nodule >1cm. you order TSH and a thyroid US. lab results return low TSH. nuclear medicine thyroid scan reveals a non-toxic goiter, nodule is not releasing excess T4. what is the next step?
FNA biopsy
(fine needle aspiration)
this is very unusual for it to be not “hot”, non-toxic
pt presents with clinically evident thyroid nodule >1cm. you order TSH and a thyroid US. Lab results return a normal TSH. what is the next step?
refer for FNA biopsy (fine needle aspiration)
one of the most common causes of asymptomatic hypercalcemia in an otherwise well adult?
primary hyperparathyroidism
hypothalamic-pituitary-thyroid axis
hypothalamus releases TRH (thyroid hormone releasing hormone) –> stimulates anterior pituitary to release TSH (thyroid stimulating hormone) –> stimulates the thyroid to produce T3 and T4
TSH production requires which nutritional components (3)
- protein
- magnesium
- zinc
T4 production requires which nutritional components (3)
- iodine
- vitamin C
- vitamin B2
T3 production requires which nutritional and body system requirements
- selenium
- healthy liver function
- healthy adrenal gland function
hyper vs. hypothyroid: which can you treat as NP in primary care vs. which do you refer out?
NP can treat hypothyroid (levothyroxine replacement)
refer out hyperthyroid for consultation
what is deQuervein’s thyroiditis?
aka subacute granulomatous thyroiditis
transient thyroid inflammation (hyperthyroidism, transient) usually s/t a viral infection
possible physical exam findings indicative of hyperthyroidism
- thyroid bruit
- exophthalmos
- hyperactive DTRs
- tachycardia
- proximal muscle weakness
- lid lag
- atrial fibrillation
world-wide most common cause of hypothyroidism
iodine-deficiency (uncommon in US)
% of hypothyroidism that is caused by Hashimoto’s autoimmune thyroiditis?
90-95%
(3) most common causes of hypothyroidism
- autoimmune Hashimoto’s
- ablative therapy for hyperthyroidism treatment
- iodine deficiency
role of PTH (parathyroid hormone) in the body
increases serum calcium
opposite of calcitonin
what is primary hyperparathyroidism
elevated level of parathyroid hormone (PTH)
excess PTH = hypercalcemia
caused by overactivity of one or more of the four parathyroid glands, via enlargement (hyperplasia), adenoma (benign tumor), or malignant tumor
clinical presentation of primary or secondary hyperparathyroidism
variable
“moans, groans, stones, and bones with psychic overtones”
common s/s include:
- loss of energy
- poor concentration or memory
- depression
- OSTEOPOROSIS/OSTEOPENIA
- insomnia
- GERD
- decreased libido
- hair loss
- bone and joint aches
other s/s:
- kidney stones
- hypertension
- arrhythmias, atrial fibrillation
- liver dysfunction
- abnormal blood protein levels
diagnostic evaluation of primary hyperparathyroidism
elevated serum calcium found on labs without other obvious cause
confirmed by elevated PTH level
additional test could include a 24-hour urine calcium to determine disease severity – specialty consult advised
priority sequelae of primary hyperparathyroidism
osteoporosis
what is secondary hyperparathyroidism
elevated PTH as a result of another condition that lowers serum calcium levels, thus causing the parathyroid glands to overproduce PTH
causes include:
- severe calcium deficiency
- severe vitamin D deficiency
- chronic kidney disease
most common causes of secondary hyperparathyroidism (3)
- calcium deficiency
- vitamin D deficiency
- chronic kidney disease
diagnostic evaluation of secondary hyperparathyroidism
low-normal serum calcium
elevated PTH on labs
presence of severe renal dysfunction (often on dialysis or have significant kidney problems over several years)
treatment options for hyperparathyroidism
- surgery to remove the problematic gland is curative 95% of the time for primary hyperparathyroidism, only considered as last resort in secondary
- cinacalcet (Sensipar) is a calcimimetic used to treat hyperparathyroidism in CKD or parathyroid cancer, causes less parathyroid hormone to be released
- bisphosphonates and/or hormone replacement therapy for post-menopausal women should be considered to prevent bone loss
- phosphate binders and/or vitamin D analogs can be used in secondary hyperparathyroidism if vitamin D deficiency or calcium deficiency is the cause
- ensure adequate intake of vitamin D and calcium
- stop use of lithium or thiazide diuretics which may exacerbate
avoid use of (2) medications in someone with hyperparathyroidism as these can elevate levels of both PTH and calcium, exacerbating the condition
- thiazide diuretics
- lithium
if a patient is taking either of these (2) medications when hyperparathyroidism is found on labs, they should stop medications and have calcium levels reassessed after a medication-free interval to confirm the diagnosis
lithium or thiazide diuretics (e.g., HCTZ)
