Thyroid Flashcards
What does the thyroid make more of, T3 or T4?
T4
How is T3 & T4 transported?
Protein bound & freely
Does the protein bound hormone exhibit biologic effects?
No, only the free hormone
What is the role of thyroid hormone, especially at birth?
Crucial for cell differentiation – if absent at birth can cause severe mental retardation = “creatinism”
What is the role of thyroid hormone as an adult?
Helps maintain thermogenic and metabolic homeostasis in the adult. Also essential for normal metabolism, protein synthesis and organ function
How much iodine do we need on a daily basis?
0.2mg
Most commonly, thyroid disorders are what type of disorder?
Autoimmune process
What type of history questions should you ask someone who you suspect has a thyroid disorder?
visual changes, skin/hair, mood changes, energy level, palpitations, constipation/diarrhea, weight changes, fluid retention, heat/cold intolerance.
What must you always check on PE in someone you suspect with a thyroid disorder?
visual/eyes, weight, scalp/hair, neck, skin, heart, abdomen, extremities, reflexes and thyroid exam neuro
What are the most informative test for thyroid function?
Thyroid stimulating hormone (TSH) and free T4, sometimes free T3
Which test is an extremely sensitive indicator for thyroid function?
TSH – almost always abnormal with hyper/hypothyroid states
What controls the secretion of TSH?
Negative feedback from thyroid hormones
What’s the normal range for TSH?
0.27-4.2
If TSH is low, what does that usually indicate?
Primary hyperthyroidism
If TSH is high, what does that usually indicate?
Hypothyroidism
If the TSH is normal does it always rule-out hypo/hyperthyroidism?
No - on very rare exceptions
What if a patient’s TSH is in the 3-6 range?
Should follow for the development of hypothyroidism
What’s the goal TSH level is someone with hypothyroidism?
So, in what type of patients should we always check TSH levels?
Prenatal, mood disorder, Afib, weight changes, dementia/delirium, and dyslipidemia
If TSH, is such a good test, why would we check T4?
Occasionally needed to confirm hypo/hyperthyroidism, and useful in management of thyrotoxicosis
What’s the normal ranges of Free T4?
9-24
When would we check a T3?
If TSH is low, but Free T4 is normal and patient presents clinically with hyperthyroid → check T3 (total & free)
You said, that many thyroid diseases are autoimmune based… so then what tests would you do to confirm autoimmune thyroid disease?
Anti-thyroid antibodies
When would the anti-thyroid antibodies be elevated?
Hashimoto’s thyroiditis and Graves disease
What do TSH-receptor antibodies detect, what is it also known as, and what does it do?
Detects – IgG AKA – TSI (thyroid stimulating immunoglobulin)
It stimulates hormone production and is elevated in Graves disease
If a patient presents with increasing fatigue, weight gain, with dry skin, and losing hair, what diagnosis do you think?
Hypothyroidism
What is hypothyroidism?
Autoimmune, AKA Hashimoto’s Thyroiditis
What causes Hypothyroidism?
Idiopathic, can occur post radioactive iodine, congenital (screen newborns), or drug induced
Lymphocytic infiltration of the gland – early phase may be hyperthyroidism (from stored hormone) but end results is hypothyroidism
What are some early symptoms of hypothyroidism?
Fatigue, lethargy, weakness, cold intolerance, constipation, dry skin, hair loss, HA, and menorrhagia
What are some late symptoms of hypothyroidism?
Slow speech, muscle cramps, hoarse voice, weight gain, amenorrhea
What are some PE findings of early hypothyroidism?
Thin, brittle nails; thin, dry hair; delayed deep tendon reflex
What are some PE findings of late hypothyroidism?
Goiter, facial/eyelid puffiness, alopecia, bradycardia, edema (non-pitting!), pleural/pericardial effusions
If the PE finding shows abnormal interstitial accumulation in skin giving it a waxy/coarsened appearance – what is this known as?
Myxedema
What might you see on labs with hypothyroidism?
Increased TSH, decreased FT4, elevated triglycerides, low HDL, anti-thyroid antibodies
What would be a late lab finding of Hypothyroidism?
Anemia & Elevated LFT’s
How do you treat hypothyroidism?
Levothyroxine – Initiate 50-100ug/day and titrate towards full dose over time
What must we do when we start a patient on Levothyroxine treatment?
Follow their TSH levels – every 2-3 months, until normal (0.5-2.5)
What is our goal when treating a patient with hypothyroidism?
Symptoms improve slowly (months)
Will the lipids improve with levothyroxine in a patient with hypothyroidism?
They will improve a little but lipid meds usually needed
How do we prevent and treat congenital hypothyroidism?
Early detection! Replacement therapy (10-15)
If a patient presents with unexplained weight loss, fatigue, who often feels hot and anxious – what diagnosis are you thinking?
Hyperthyroidism
What else is hyperthyroidism known as?
Thyrotoxicosis
What is the most common etiology of hyperthyroidism?
Graves disease
What are other etiologies for hyperthyroidism?
Toxic (“hot”) adenomas, early phase hasimoto’s (from stored hormone), factitious (excessive thyroid hormone intake), TSH adenoma, or amiodarone
What is Graves disease?
Autoimmune disease, caused by TSH-receptor antibody (IgG) causes hypersecretion, hypertrophy, and hyperplasia of the thyroid (goiter)
What are some of the symptoms associated with hyperthyroidism?
Hyperactivity, irritability, heat intolerance, sweating, palpitations, fatigue, weakness, increased appetite, weight loss, diarrhea, oligomenorrhea
What might you find on PE with hyperthyroidism?
Tachycardia, arrhythmias, fine tremor, goiter/bruit, oily fine hair, proximal muscle weakness, opthalmopathy, dermopathy, and hyperreflexia
What would the labs show with hyperthyroidism?
Very low TSH (often
What type of hyperthyroidism that occurs in 2-5% of patients do we need to remember?
T3 thyrotoxicosis
What 2 signs & symptoms are unique to Graves disease?
Opthalmopathy – Proptosis with lid-lag, conjunctival inflammation and corneal drying
Dermopathy – pre-tibial areas leading to edema, thickened skin (pre-tibial myxedema)
What are some complications of Graves disease?
Cardiac arrhythmias – Afib! Thyroid storm
How can we treat Graves disease?
MUST have an endocrinologist consult
Propranolol (heart)
Thiourea drugs = Propylthiouricil (PTU) or Methimazole – inhibits thyroid peroxidase and block organification of iodine.
What are some of the side effects of Thiourea drugs?
Agranulocytosis and pruritis. Must follow WBC & Free T4
Must monitor for liver injury!
Cannot use in 1st tri of pregnancy (due to birth defects)
If a patient with Graves disease stops returns to normal levels and then stops treatment, what can occur?
Recurrent thyrotoxicosis in 50%
What is the definitive treatment of choice for Grave’s disease in the US?
Radioactive iodine (131I) – destroy overactive thyroid tissue
What must we monitor when giving RAI for grave’s disease? Why?
Follow free T4.
Permanent hypothyroidism often develops within one year, thus thyroid replacement therapy needed for life. Can’t use in pregnancy!
What may worsen after giving RAI for grave’s disease?
Opthalmopathy; especially in smokers
When would thyroid surgery be indicated?
Graves in children or hyperthyroidism during pregnancy that can’t be control with thiourea drugs.
For patients with Grave’s that have failed 131I
What must you do if you notice a nodule on a patient’s thyroid?
Must do a fine needle aspiration to R/O cancer
A thyroid nodule may be benign, but what can it cause?
Thyrotoxicosis (Toxic thyroid nodule)
How do you treat a toxic thyroid nodule?
RAI if >40
Surgery or RAI if
If a fine needle aspiration is done on a nodule and thyroid cancer is determined, what type of thyroid dysfunction would they have?
None!
What does thyroid cancer feel like?
A firm, non-tender nodule
How do you treat thyroid cancer?
Near total thyroidectomy, post-op suppress TSH, follow-up with total body RAI
