Labs Flashcards
Free T4 (thyroxine)
- Most accurate reflection of thyrometabolic status
- Difficult to measure
- Assessed in confounding non thyroidal illnesses
Total serum T4 (Throxine )
- Initial screening test to assess thyroid fxn
- High in hyper, low in hypo
- Measures free & bound
Serum T3 (Triiodothyronine) resin uptake
- Thyroid hormone binding ratio
- Indicates number of binding sites on thyroid binding protein
- Low when concentration of of thyroid binding protein is high
- Radiolabeled T3
Total serum T3 Triiodothyronine
- Indicator of hyperthyroid
- Low in malnutrition, cirrhosis & uremia
Thyroid stimulating hormone
- Measure response to levothyroxine tx
- Elevated in hypothyroid, decreased in hyperthyroid
- Secreted from anterior pituitary
Radioactive iodine uptake test
- Assessment of intrinsic fxn on thyroid gland
- Ability of thyroid to trap and concentrate iodine
- Distinguish hyperthyroid causes
- Hot spots in thyrotoxicosis, iodine deficiency
- Affected by store of iodine
Antithyroid antibodies
- Hasimoto & Graves disease
- Not necessary for dx
Follicle stimulating hormone
- Increases in puberty prior to LH
- Distinguish primary versus secondary gonadal sufficiency
- Increased in menopause, ovarian failure
- Decreased in adenomas, ovarian tumors
Luteinizing hormone
- Surge causes ovulation
- Increased in ovarian failure menopause
- Decreased: pituitary adenomas, and eating disorders
Estradiol
- Evaluation of menstrual and fertility
- Estriol elevated in pregnancy
- Estradiol elevated tumors, menstruation, pregnancy and ovulation
Testosterone
- Elevated with female virilization, adrenal neoplasms, hirsutism, adrenal hyperplasia, ovarian tumors
- Draw early AM- at peak
- Decreased in hypogonadism in males
Human chorionic gonadotropin
- Indication of pregnancy
- Tumors of ovaries, testies, gonads
Thyroid autoantibodies
Elevated in graves and hashimotos disease
- Evidence of autoimmune disorders
Serum thyroglobulin
- Precursor protein for thyroid protein synthesis
- Marker for thyroid cancer
- Elevated in overactive thyroid
Antithyroperoxidase antibodies
- Elevated in Hashimoto (95%) & Graves and 10% with out thyroid disease
Antithroglobular antibodies
- Elevated ratio in active hashimotothroiditis
Fine needle aspiration biopsy
Differentiation of benign and malignant tumors
- Dx malignancy in nodules
Thyroid US
Assess characteristics of nodular lesions- malignant v benign
- Size, differentiate solid nodules from cystic lesions
- Guide for biopsy
Calcium
- Elevated in primary hyperparathyroid & malignancy
- Decreased in hypoalbuminemia, Vit D deficit, hypoparathyroid, pseudohypoparathyroid
Magnesium
- Hyper impairs release of PTH
- Increased real loss, hyperPT, hyperthyroid
- Hypo associated with CKD
Phosphate
Hyper: Vit D deficiency, osteomalacia, hyperPT, hyperthyroid, hypercalcemia
Hypo:Advance CKD, hyperVit D, pseudohypoPT
