Endocrinology Flashcards
What are the common symptoms and signs of hyperthyroidism?
Sx: nervousness, anxiety, irritability, insomnia, heat intolerance, sweating, palpitations, tremors, weight loss with increased appetite, fatigue, weakness, emotional lability, diarrhea
Signs: enlarged thyroid, warm skin, thyroid “stare”/lid lag, exophthalmos, proptosis, opthalmoplegia (Graves), pretibial myxedema (Graves), tremor, tachycardia, a. fib (check TSH in pts with new-onset a. fib)
What are the most common causes of hyperthyroidism?
- Graves disease (diffusely enlarged thryoid, + thyroid-stimulating Ig and Abs, exopthalmos, proptosis, ophthalmoplegia, pretibial myxedema)
- Toxic multinodular goiter in elderly (“hot” nodules on thyroid nuclear scan)
- Adenoma (single “hot” lump)
- Subacute thyroiditis (viral infection with TENDER thyroid)
- Factitious hyperthyroidism (pt taking thyroid hormone)
RARE CAUSES: amiodarone (hypo- or hyperthyroidism), TSH-producing pituitary tumor, thyroid CA, struma ovarii (ovarian teratoma)
Describe the lab findings in hyperthyroidism
Decreased TSH (unless pt has TSH-secreting tumor), increased triiodothyronine (T3) and thyroxine (T4)
How is hyperthyroidism treated?
Short-term (stabilizing) tx: propylthiouracil (PTU) and methimazole/carbimazole are suppressive agents, beta-blockers for thyroid storm, iodine can suppress thyroid but rarely used for this clinically
Definitive (curative) tx: radioactive iodine ablation, surgery preferred for pregnant pts = both result in hypothyroidism so hormone replacement for life is necessary
What are the symptoms and signs of hypothyroidism?
Sx: weakness, lethargy, fatigue, cold intolerance, weight gain with anorexia, constipation, loss of hair, hoarseness, menstrual irregularity (classically menorrhagia), myalgias and arthralgias, memory impairment, dementia
Signs: bradycardia, dry/coarse/cold/pale skin, periorbital and peripheral edema, coarse/thin hair, thick tongue, slow speech, decreased reflexes, HTN, carpal tunnel syndrome and paresthesias, autoimmune associations (vitiligo, pernicious anemia, DM), coma
- Cretinism in children (mental, motor, and growth retardation)
What are the common causes of hypothyroidism?
- Most common cause is Hashimoto thyroiditis (women of reproductive age outnumber men by 8:1) - lymphocytes plus antithyroid and antimicrosomal Abs, nontender goiter
- Second most common cause is iatrogenic after tx of hyperthyroidism
- Others: iodine deficiency, amiodarone, lithium, secondary hypothyroidism due to pituitary or hypothalamic failure (decreased TSH) e.g. Sheehan syndrome
Describe the lab findings in hypothyroidism
Increased TSH (unless 2/2 secondary causes), decreased T3 and T4 Hashimoto thyroiditis: antithyroid and antimicrosomal Abs
Why is free T4 (or free T4 index) better than total T4 for measuring thyroid hormone activity?
Free T4 measures the active form of thyroid hormone. Many conditions change the amount of thyroid-binding globulin (TBG), thus changing total T4 levels (e.g. pregnancy, estrogen therapy, OCPs all increase TBG; nephrotic syndrome, cirrhosis, corticosteroid tx all decreased TBG)
T3 resin uptake is an older tests - should rise or fall in same way as free T4
How is hypothyroidism treated?
T4 or thyroxine. T3 should not be used. In elderly pts, “start low and go slow” because overtreatment is dangerous.
What is euthyroid sick syndrome?
Any pt with any illness may have temporary derangements in thyroid fxn tests that resemble hypothyroidism. TSH ranges from normal to mildly elevated, serum T4 ranges from normal to mildly decreased.
What are the symptoms and signs of Cushing syndrome (increased corticosteroids)?
Sx: weight gain, easy bruising, acne, hirsutism, emotional lability, depression, psychosis, weakness, menstrual changes, sexual dysfunction, insomnia, memory loss
Signs: buffalo hump, truncal and central obesity with wasting of extremities, round plethoric facies, purplish skin striae, weakness (esp. proximal muscles), HTN, depression, psychosis, peripheral edema, poor wound healing, glucose intolerance or DM, osteoporosis, hypokalemic metabolic alkalosis (2/2 mineralocorticoid effects); stunted growth in children
What causes Cushing syndrome?
Most common cause is iatrogenic. 2nd most common cause is Cushing disease (pituitary adenoma secreting ACTH) causing ~60% of non-iatrogenic cases. Women of reproductive age outnumber men by 5:1.
Other: ectopic ACTH (e.g. small cell lung cancer - more common in men) and adrenal adenomas or CA (more common in children)
How is Cushing syndrome diagnosed?
24-hour free cortisol in urine or dexamethasone suppression test (cortisol not appropriately suppressed several hours after administration).
*ACTH is elevated in Cushing disease but decreased with adrenal adenoma!
If ACTH increased, MRI should be obtained to look for pituitary adenoma. If ACTH decreased and pt has no history of steroid intake, CT should be obtained to look for adrenal tumor.
What is the most common type of hypoadrenalism?
Secondary (iatrogenic) due to steroid tx. People removed from long-term steroid tx may be unable to secrete appropriate amount of corticosteroids in response to stress for up to 1 year. Watch out for classic post-op pt who crashes (hypotension, shock, hyperkalemia) and has history of a dx requiring steroid tx within the past year. Assess ACTH (high) and cortisol (low) levels but do NOT wait for results to give steroids. Give prophylactic stress doses of corticosteroids in the setting of illness, operation, or other stressor to prevent problems.
What are other causes of hypoadrenalism (other than iatrogenic)?
Most common primary cause is autoimmune (idiopathic) disease. Pt may have other autoimmune diseases (e.g. hypothyroidism, prenicious anemia, vitiligo, DM, hypoparathyroidism). Other causes include metastatic CA (esp. lung CA), infection (TB, fungal, opportunistic in AIDS or immunocompromised states), ketoconazole, and pituitary/hypothalamic failure.
