3 roles of TSH?
Attaches to TSH receptor on follicular cell Stimulates T4 and T3 secretion Stimulates thyroid gland growth (trophic effect)
3 causes for Increased TBG levels
Pregnancy Oral contraceptives Tamoxifen
4 causes for Decreased TBG levels
Testosterone Hereditary Nephrotic syndrome Chronic liver disease (cirrhosis)
_______ provides the most accurate assessment of thyroid function and distinguishes between pituitary vs. thyroid gland disorders.
The combination of TSH and free T4
Clinically euthyroid is.....
normal TSH and normal free T4 (w or without normal free T3) regardless of total T4 or T3.
graves dz and the RAI uptake.....
diffuse increased uptake
Toxic multinodular goiter and RAI uptake.....
areas of increased and decreased uptake
subacute thyroiditis and RAI uptake?
diffuse decreased uptake *b/c the gland has been damaged and unable to makenew hormone so cant take up idoein*
thyroid nodules and RAI uptake?
Hot nodule-- incrased uptake cold nodule-- decreaed uptake
4 uses of US...
Detect nodules and cysts >3 mm. Fine needle biopsy of nodules Fine needle aspiration of cysts Follow-up thyroid cancer, e.g. spread to lymph nodes
6 causes of hypothryoidism?
1. Iodine deficiency---most common cause worldwide 2. Autoimmune disease (Hashimoto’s thyroiditis)* 3. Iatrogenic---post-treatment for hyperthyroidism* (Antithyroid drugs, radioactive iodine) 4. Drugs (Iodine excess (dietary, contrast media) Amiodarone (37% iodine by weight), Lithium) 5. Congenital (cretinism) 6. Transient---subacute thyroiditis
2 causes of secondary hypothyroidism?
Hypopituitarism Hypothalamic disease
6 lab tests for hypothyroidism?
1. TSH---best test 2. Free T4---distinguishes subclinical from clinical (Subclinical---increased TSH, normal free T4; Clinical---increased TSH, low free T4) 3. Free T3---not useful; ~25% of patients have nl. T3 4. TPO antibodies---(+) in 90% of patients 5. CPK (aka CK)---often increased 6. Cholesterol +/- triglycerides---increased
how to treat hypothryroidism?
Adjust dose every 6-8 weeks per TSH level In elderly patients and those with CAD disease adjust dose more cautiously. ** once stable can check labs yearly
Too much TSH suppression can cause.....
atrial fibrillation and osteoporosis.
Symptoms and Signs of myxedema coma?
Decreased consciousness with or without seizures Hypothermia Hyponatremia, hypoglycemia
treatment of myxedema coma?
I.V. T4 with or without T3 I.V. glucocorticoids
___ is State of thyroid hormone excess
_____ is State of thyroid hormone excess due to excessive thyroid gland function
primary hyperthyrodism causes a ____ uptake of Rai
secondary hyperthyroidism causes a _____ uptake of RAI
thyrotoxicosis with out hyperthyroidism causes a _____ uptake or RAI?
causes of primary hyperthyroidism?
Graves’ disease (MOST COMMON**) Toxic multinodular goiter Toxic thyroid adenoma Functioning thyroid cancer +/- functioning mets. Iodine excess (with preexisting thyroid dysfunction) ** low TSH
causes for secondary hyperthyroidism?
1. TSH seceting pit. adenoma (TSH is high) 2. chorionic gonadotropin secreting tumor (TSH is low )
causes of thyrotoxicosis without hyperparathyroidism?
Ingestion of excess thyroid hormone (TSH low) Thyroid destructive processes (TSH variable) Subacute thyroiditis Silent (painless) thyroiditis Radiation to thyroid
5 ways to diagnosis of graves disease?
- decrased TSH - increased Free T4 - TPO antibodies - T3 toxicosis---increased free T3, decreased TSH, nl. free T4 - Radionuclide scan---use only in equivocal cases
tx of hyperthyroidism?
- Methimazole - take 6-8 weeks to get euthyroid - relapses occur - SE-- rash, fever, urticaria, arthralgias, SLE like syndrome
What is used if a pt fails intial rx with hyperthyroidism?
- try radioactive idoine - takes 2-3 months to become euthyroid - most pts become hypothyroid in 5-10 years
what role to BB have in tx of hyperthyroidism?
Control adrenergic symptoms until antithyroid drugs or RAI work
what surgical intervention can be used to help treat hyperthyroidism? when is someone a candidate? complications?
subtotal thyroidectomy candi-- relapses after drug theraphy or refusal of RAI therapy compli-- damage to recurrent laryngeal nerve
what is the etiology of subacute thyroiditis?
sx of subacute thyroiditis?
1. Painful gland; mimics pharyngitis; URI symptoms may precede thyroid symptoms 2. Tender, asymmetrically enlarged gland 3. Sx’s progress from hyper-hypo
What does EUTHYROID SICK SYNDROME usually occur?
with acute severe illness ** avoid routine TSH testing in acutely ill pts
What are the most common labs associated with euthyroid sick syndrome?
1. Decreased total and free T3 2. Increased reverse T3 3. Mostly normal total and free T4 and TSH
what are 3 things to note with amiodarone?
Effect lasts 6 months (stored in adipose tissue) Can cause either hypo- or hyperthyroidism Monitor TSH and free T4 during chronic therapy
Cold nodule could be due to.....
a nonfunctioning thyroid cancer
_____ is the most common endocrine malignancy?
thyroid cancer F:M 2-1
what are the 3 types of thyroid cancers?
1. follicular epitherlial cell 2. C cell (medullary thyroid ca) 3. other (lymphoma, sarcoma, and metastases)
What are the 2 types of follicular epitherlial cell malignancies?
1. well-differentiated ( papillary (70-90 perc.) and follicular) 2. undifferentiated