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29 Cards in this Set
- Front
- Back
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Thyroid hormone precursors
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- Thyroglobulin
* Glycoprotein rich in Y * Iodine |
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Thyroid peroxidase (TPO)
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- An enzyme in the synthetic process
* Iodination: Monoiodothyronine and Diiodothyronine |
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Thyroid hormones
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- T3 & T4
* free forms of T3 & T4 are active (enter cell, effectors of metabolism and development) * T4 ~0.04% unbound * T3 ~0.4 % unbound |
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T3
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- 3 iodines in molecule
- 3-8x > activity than T4 referred to as the active form |
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Thyroid Binding Proteins
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1) Thyroxine binding globulin
- increased in pregnancy * total T4 & total T3 elevated * FrT4 & FrT3 normal 2) Thyroxine-binding prealbumin (TBPA) - aka Prealbumin or Transthyretin 3) Albumin - thyroid hormones distribute b/w these three |
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Calcitonin
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- also produced by thyroid gland
- a minor role in Ca/PO4 metabolism * increase associated with C-cell hyperplasia * medullary thyroid cancer (MTC) - Calcitonin levels are used to monitor the effectiveness of treatment for MTC |
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Hypothyroidism
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- 5-15 % women over 65 y.
* can lead to myopathy * increased CK, hyperlipidemia - Chronc lymphocytic thyroiditis: Hashimoto’s disease * Goiter * Autoimmune: TPO Ab, Thyroglobulin Ab - Primary: low frT4, high TSH - Secondary: low TSH, due to hypopituitarism - Tertiary: hypothalamic dysfunction (rare) |
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Hyperthyroidism
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- Thyrotoxicosis
- Grave’s disease |
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Thyrotoxicosis
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Thyroid hormone excess
1) Excess hormone ingestion 2) Leakage from thyroid follicles 3) Hyperthyroidism |
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Grave’s disease
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- Autoantibodies activate TSH receptors on thyroid follicular cells
- Symptoms: goiter, ophthalmyopathy, dermopathy more common in females elevated free T4, TT3, undetectable TSH - TSI (thyroid stimulating immunoglobulin) antibody * Diagnostically sensitive & specific * Monitor therapy, predict relapse & remission - Anti-TSH receptor antibody |
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Primary hypothyroidism Lab Test
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- low total or frT4
- Elevated TSH level |
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Primary hyperthyroidism Lab Test
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- levels of frT4 and frT3 elevated
- TSH secretion is suppressed |
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Secondary hypothyroidism
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low TSH
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Secondary hyperthyroidism
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high TSH
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All of the following statements about iodine are true EXCEPT:
A.) Iodine deficiency is one of the most common causes of hypothyroidism in the world B.) T4 has 4 iodine molecules C.) Radioactive iodine treatment of Grave's disease is effective in less than 40% of patients treated with this agent D.) Radioactive iodine uptake is often useful in determining the cause of thyrotoxicosis |
C.) Radioactive iodine treatment of Grave's disease is effective in less than 40% of patients treated with this agent
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The thyroid gland:
A.) is an ineffective iodine trap B.) depends on thyroidal peroxidase (TPO) to permit iodination of the tyrosyl residues to make MIT and DIT C.) depends on thyroidal peroxidase (TPO) to permit the joining of two DIT residues to form T3 D.) usually functions independent of TSH levels |
B.) depends on thyroidal peroxidase (TPO) to permit iodination of the tyrosyl residues to make MIT and DIT
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The thyroid gland produces all of the following EXCEPT:
A.) TSH B.) thyroglobulin C.) T3 D.) T4 |
A.) TSH
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Hypothyroidism is generally associated with all of the following EXCEPT:
A.) weight gain B.) an elevation of TSH levels C.) TPO antibodies D.) TSH-receptor antibodies |
D.) TSH-receptor antibodies
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Parathyroid hormone (PTH)
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- Regulate Vitamin D metabolism
- Maintain plasma Ca and PO4 in normal range - PTH intact: PTH IRMA (IRMA: immunoradiometric assay) * responds to low [Ca] * stimulation of bone resorption |
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Organ “contribution” to
calcium homeostasis |
1.) Small intestine
2.) Bone - osteoclasts: cells associated with remodeling & repair of bones (bone resorption) - osteoblasts: cells associated with the formation of bone 3.) Kidneys - renal failure: major cause of disordered calcium metabolism * failure to synthesize 1,25-OH Vitamin D |
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Multiple Myeloma
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bone destruction
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Pagets disease
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excessive bone resorption
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Calcium absorption
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- enhanced by 1-25 Vitamin D
- inhibited by dietary phosphate * high phosphate diets (SODAS AND FAST FOODS) |
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Calcium methods, Total & Ionized determinations
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- Total: dye binding
- pH dependency: As pH increases, more Ca is bound to albumin - Uncapped venous serum: inc pH, more Ca bound to albumin |
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Hypercalcemia
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1.) Hyperparathyroidism
2.) excess PTH 3.) PTHrP |
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Hyperparathyroidism
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- adenoma(s), hyperplasia
- hyperplasia may be sporadic or due to a genetic syndrome |
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excess PTH
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- increases tubular calcium reabsorption
- net calcium excretion increased |
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PTHrP
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- hypercalcemia associated with some malignancies
- produced by some tumors, NOT the parathyroid |
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Hypocalcemia
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- Hypoparathyroidism, Vitamin D deficiency
- Secondary hyperparathyroidism * renal insufficiency or failure * Parathyroid's healthy, PTH elevated |
