08 Thyroid Disorders Quan Flashcards
What are the thyroid hormone functions?
Growth and development (long bone growth and neuronal maturation). Increase basal metabolic rate. Body temperature. Body homeostasis
What are the main steps in Thyroid Hormone Synthesis?
Hypothalamus releases thyrotropin-releasing hormone (TRH) to stimulate anterior pituitary. Pituitary releases thyroid stimulating hormone (TSH) to activate the thyroid gland. Thyroid gland produces T3/T4
For thyroid hormone regulation, what happens with Low T4/T3 levels?
Stimulates release of TRH from hypothalamus
For Thyroid Hormone Regulation, what happens with High T4/T3 levels?
Regulate negative feedback loop. Decrease production of TRH and TSH
What is Thyroxine?
T4
What is Triiodothyronine?
T3
What is the major circulating thyroid hormone?
T4, secreted by the thyroid
Which thyroid is more potent?
T3 is 4x more potent than T4
What is the half-life like for thyroid hormones?
T4 7 days. T3 1.5 days
What are the T3 concentrations like?
T3 has lower serum concentration than T4 (80% of T3 from T4 –> T3 conversion in the periphery)
What are the normal TSH concentrations?
0.5-5 milliinternational units/L
What are the TSH concentrations like in Hyperthyroidism?
Low
What are the TSH concentrations like in Hypothyroidism?
High
What are the normal Free T4 concentrations?
0.8-2.7 ng/dL
What are the Free T4 concentrations like in Hyperthyroidism?
High
What are the Free T4 concentrations like in Hypothyroidism?
Low
What are the normal Total T4 concentrations?
4.5-10.9 mcg/dL
What are the Total T4 concentrations like in Hyperthyroidism?
High
What are the Total T4 concentrations like in Hypothyroidism?
Low
What are the normal Total T3 concentrations?
60-181 ng/dL
What are the Total T3 concentrations like in Hyperthyroidism?
High or normal
What are the Total T3 concentrations like in Hypothyroidism?
Low or normal
What is the normal range for Thyroperoxidase (TPO)?
< 100 IU/mL
What are the normal Antithyroglobulin (ATgA) levels?
< 8%
What are the normal Thyroid Receptor Antibodies (TRAb) titers?
Titers Negative
What is the definition of Hyperthyroidism?
Heterogeneous group of disorders characterized by elevated levels of thyroid hormones in the blood
What is Graves Disease?
Most common cause of hyperthyroidism. Defect in the autoimmune system. Antibodies attack thyroid gland –> hypertrophy and overproduction of thyroid hormone. Antibodies also attack eye muscles and pertibial skin (causing bulging eyes)
How does Hashimoto’s differ from Graves disease?
Hashimoto’s disease is also an autoimmune disease, but causes atrophy instead of hypertrophy of the cells, causing hypothyroidism
What are some drugs that can cause Hyperthyroidism?
Amiodarone. Lithium. Iodines. Interleuin. Interferon-a
What are the lab findings like for Subclinical Hyperthyroidism?
Low TSH. Normal T3 and T4
What are the Subjective Signs of Hyperthyroidism?
Heat intolerance. Weight loss. Amenorrhea. Diarrhea. Photophobia. Palpitations. Nervousness, irritability, insomnia. Fatigue, weakness
What are the Objective Signs of Hyperthyroidism?
Goiter (bruits, thrills). Proximal muscle weakness on physical exam (d/t decrease in serum K). Tremor on physical exam. Proptosis (bulging eyes). Thinning of hair. Tachycardia. Wide pulse pressure. Palmar erythema. Pretibial myxedema
What is the preferred treatment for Hyperthyroidism?
Radioactive Iodine Therapy (I^131). For patients with cardiac disease, elderly, toxic multinodular goiter, failed thioamides, ophthalmopathy. Safe, but can lead to chronic hypothyroidism!!!
What are the contraindications for Radioactive Iodine Therapy?
Pregnancy. Breast feeding. Thyroid cancer
How can pre-treatment with thioamide help?
Decreases stored hormones. Decreases risk of worsening hyperthyroidism. Consider in elderly patients and patients with cardiac disease
When is surgery usually considered for hyperthyroidism?
Not commonly used, with exception of thyroid cancer. Reserved for patients non-responsive or intolerant to antithyroid medications. Patients with large thyroid goiters resistant to I^131. Pregnant patients
What are the complications of surgery for hyperthyroidism?
Hypoparathyroidism. Vocal cord paralysis
What are the pharmacological treatment choices for hyperthyroidism?
Thioamides. Iodide products
What are the Thioamides used for Hyperthyroidism?
Methimazole (Tapazole). Propylthiouracil (PTU)
What is the MOA of Thioamides?
Inhibits synthesis of thyroid hormones by inhibiting thyroid peroxidase-catalyzed reactions required for iodine oxidation. Inhibits the coupling of iodotyrosines. PTU inhibits peripheral conversion of T4 –> T3