Case 5: Palpitations Flashcards
Hyperthyroidism pathophysiology
Increased T3/T4 that causes symptoms due to
a) thyroid hormone’s stimulation of catabolism
b) enhancement of sensitivity to catecholamines
Hyperthyroidism signs in pts under 50 (9)
- heat intolerance
- tachycardia
- fatigue
- weight loss
- tremor
- increased sweating
- exertional dyspnea
- decreased menses
- diarrhea
Older patients (>70) symptoms of hyperthyroidism
- sinus tachycardia
- fatigue or insomnia
- asymptomatic
exophthalmos = proptosis
Most often seen in Grave’s
either bilateral or unilateral
Causes of enlarged thyroid = goiter
- lack of iodine
- hypothyroidism
- hyperthyroidism
- nodules (single or multiple)
- thyroid cancer
- pregnancy
- thyroiditis
Lack of iodine
Worldwide most common cause of goiter and also causes developmental delay and mental retardation
- most affected in N Africa and Pakistan
- prevent with supplemental iodine
Clonus
Series of abnormal reflex movements of the foot induced by sudden dorsiflexion causing alternate contraction and relaxation of gastrocnemius and soleus muscles
HPA axis effect on thyroid
Hypothalamus secretes TRH which stimulates pituitary to produce TSH which stimulates thyroid gland to release T3 and T4
TSH increased
T4 decreased
Hypothyroidism
TSH mildly elevated
T4 normal
Subclinical hypothyroidism
TSH normal
T4 increased
Pituitary adenoma (TSH producing) OR thyroid hormone resistance - need to assess Sx further
TSH decreased
T4 increased
Hyperthyroidism
TSH decreased
T4 decreased
Central hypothyroidism (TRH deficiency) or Pituitary hypothyroidism (TSH deficiency)
TSH decreased
T4 normal
T3 increased
T3 toxicosis
Primary symptoms of eye manifestations of Graves
Related to corneal irritation from eyelid retraction
Special info about exopthalmos
- While 50% of patients with Graves’ have some eye involvement by MRI, only about 20-30% of those are clinically relevant.
- In up to 10% the eye manifestations can happen when the patient is euthyroid or even
hypothyroid. - Treatment of hyperthyroidism does not affect the eye manifestations.
- In fact, in some
patients who get radioactive iodine, will experience worsening symptomatology.
Graves’ Disease
- autoimmune disease in which thyrotropin receptor Abs (thyroid stimulating Igs) are produced –> make more thyroid hormone
Graves’ epidemiology
- women 5-10x more likely to get it
- peak incidence between 40-60
- often occurs w family Hx of thyroid disease
- can be associated with other autoimmune diseases
Graves’ triggers include (3)
- stressful life events
- high iodine intake
- recent pregnancy
Sx of hypothyroidism (5) due to slow metabolism
- weight gain
- cold intolerance
- pedal edema
- heavy periods
- fatigue
Fatigue present in hyper, hypo, or both
Present in both hyper and hypothyroidism
How to elicit lid lag
- patient follows your finger w eyes: move finger from upper to lower field of vision - upper eyelid will lag behind upper edge of iris as eye moves downward
Pay special attention to Hx if (2)
- teenager was giving history of abstinence in presence of parent
- partner in room
Cardiac causes of palpitations
- arrhythmia
- cardiomyopathy
- hypovolemia
Psych causes of palpitations
- anxiety
- panic attacks
Med causes of palpitations
- caffeine
- stimulants
- theophylline
- albuterol
Substance causes of palpitations
- tobacco
- caffeine
- alcohol intox
- alcohol withdrawal
- cocaine
Endocrine causes of palpitations
- hyperthyroidism
- pheochromocytoma
- hypoglycemia
Hematologic causes of palpitations
- anemia
Infectious causes of palpitations
- febrile illness
Cardiac arrhythmias
- cause palpitations when HR is fast
- can be assoc with dizziness or SOB
How to differentiate anxiety/panic disorder from hyperthyroidism
Hyperthyroidism will have presence of systemic symptoms such as weight loss, changes in stool, changes in menses
Anemia causes palpitations because of…
Associated with…
- sinus tachycardia due to reduced oxygen carrying capacity in blood (also causes dyspnea this way)
- positional dizziness (unlike hyperthyroidism)
Causes of anemia
- weight loss leading to nutritional deficiencies (B12, folate)
- malignancy
- heavy periods
- bleeding from GI tract
Palpitations due to drugs(meth, cocaine)/caffeine
- pupil dilation
- increased energy
- increased BP
- erratic behavior
Common causes of hyperthyroidism (5)
- Toxic diffuse goiter
- Toxic nodular goiter
- Thyroiditis
- Excessive iodine ingestion
- Drug induced hyperthyroidism
Toxic diffuse goiter (Grave’s)
Autoimmune disease: antibody acts @ TSH receptor –> gland synthesizes excess thyroid hormone
Features include:
- hypervascularity of thryoid that results in bruit or thrill upon auscultation
- Exophthalmos
- Pretibial myxedema (deposition of hyaluronic acid in dermis and subcutaneous tissue)
Toxic nodular goiter
Older patients have multinodular disease
Younger patients have solitary nodules (can be associated with iodine deficiency)
Excessive iodine ingestion
Through diet or drug: amiodarone
This can induce thyroiditis
Radioactive iodine uptake test and scan
Measures amount of radioactive iodine taken up by the thyroid in 24 hrs - allow for differentiation between various etiologies of hyperthyroidism
Normal RAIU uptake
15-30% of ingested dose
High RAIU (>30%)
Increased creation of thyroid hormone results in increased radioactive iodine uptake used to synthesize thyroid hormone
- Graves
- Active nodules
- TSH secreting pituitary tumor
- HCG secreting tumor
Low RAIU (<15%)
Excess circulating thyroid hormone in thyroiditis leads to leakage of hormone so radioactive iodine is low
- thyroiditis
- exogenous L thyroxine
- struma ovarii
- amiodarone
Studies not used to determine etiology of hyperthyroidism
Ultrasound, MRI
Ultrasound of thyroid indicated for
Evaluation of nodules and thyroid enlargement (but not hyperthyroidism), stratify risk of malignancy, guide FNA
Starting to use color flow Doppler ultrasound to replace RAI when it is not available or contraindicated
Pregnancy and thyroid treatment
PTU first trimester
Methimazole after
Most commonly used medication to suppress thyroid function
Methimazole
Methimazole side effects
Agranulocytosis: bone marrow stops producing white blood cells - patient is vulnerable to serious infecitons
How long does it take to suppress thyroid production in hyperthyroid patients?
3 months, but symptom relief typically occurs within one month
Hyperthyroid patients need to stay on medications for…
Several years - more than 1/2 will return to hyperthyroidism if they try to stop medications
Treatment of Graves’ disease
1) Meds such as methimazole or PTU (Europe)
2) Oral dose of radioactive iodine (US)
Radioactive iodine
Alternative to thyroid hormone suppressant medication
Iodine destroys most overactive thyroid cells - the level of thyroid hormone falls and the gland shrinks in size
- may have too little functioning thyroid and need thyroid hormone replacement - warn patients of hypothyroid symptoms
- once TSH is in normal range, can check once yearly
Radioactive iodine precautions with pregnancy
- obtain pregnancy test first
- patients should not be near pregnant women or young children several days following radioactive iodine treatment bc it is secreted in urine or stool - it will have bad effects on exposed kids thyroids
Radioactive iodine side effects
- transient soreness of neck or brief worsening of symptoms but should resolve in few days
- worsening eye sx in pts w opthalmopathy
Draw TSH post radioactive iodine..
once every 2-3 months until it stabilizes
- once in normal range, check once yearly
Thyroid replacement thyroid
Thyroxine in primary hypothyroidism (this is what follows radioactive treatment)
How to dose and manage thyroxine in hypothyroid patient
- 1.5-1.8 mcg/kg
- increase dose slowly
- repeat TSH in 6 weeks
- when stable TSH level achieved, check TSH 1-2/year
Note: some people who have RAI will have enough thyroid left to relapse - occasionally they need a second treatment
