Hyperthyroidism

TRH –Thyrotropin-releasing hormone  Produced by Hypothalamus  Release is pulsatile  Downregulated by T 3  Travels through portal venous system to adenohypophysis  Stimulates TSH formation

TSH – Thyroid-stimulating hormone  Produced by Adenohypophysis  Upregulated by TRH  Downregulated by T 4, T 3  Travels through portal venous system to cavernous sinus, body.  Stimulates: Iodine uptake Growth of thyroid gland

Thyroid Hormone  Majority of circulating hormone is T % T 4 1.5% T 3  Total Hormone load is influenced by serum binding proteins Albumin 15% Thyroid Binding Globulin 70% Transthyretin 10%

Hyperthyroidism  Primary hyperthyroidism  Secondary hyperthyroidism (TSH)  Tertiary hyperthyroidism (TRH)

Hyperthyroidism  Normal Thyroid  Inactive Thyroid  Hyperactive Thyroid

Hyperthyroidism  1. Graves’ disease  Toxic multinodular goiter  Toxic adenoma

Graves’ disease  Most common cause of thyrotoxicosis  Autoimmune condition with anti-TSH antibodies  Onset of disease may be related to severe stress which alters the immune response

Graves’ disease Etiology:  Is most often seen in women years of age  Toxic nodular goiter  Toxic adenomas  Subacute thyroiditis

Graves’ disease - History  Weight loss  Increased appetite  Heat intolerance, increase sweating  Nervousness  Weakness  Increased bowel frequency  Menstrual abnormalities

Graves’ disease – Clinical features  Warm, moist skin  Goiter  Sinus tachycardia or atrial fibrillation  Thyroid bruit  Tremor  Hyperactive reflexes

Graves’ disease - Exophthalmos Proptosis and lid retraction results from: 1) lymphocytic infiltration 2) edema of the extraocular muscles

Graves’ disease - Evaluation  Suppressed TSH  Elevated Total T 4  TRH  Increased free T 3, T 4  Thyroglobulin  Antibodies: Anti-TSH

Graves’ disease - Treatment 1. Beta blockers for symptoms 2. Thionamide medications  May re-establish euthyroidism in 6-8 weeks  40% - 60% incidence of disease remission 3. Radioiodine ablation  10% incidence of hypothyroidism at 1 year  55% - 75% incidence of hypothyroidism at 10 years

Graves’ disease - Treatment Surgery  Used for compressive symptoms  Hypothyroidism occurs in up to 70% of subtotal thyroidectomy patients  Pre-surgical stabilization with thionamide medications

Hyperthyroidism - Treatment Antithyroid drugs:  Methimazole  Carbimazole  Propylthiouracil

Complications Thyroid storm – extreme hyperthyroidism Symptoms include: high fever, dehydration, tachycardia high-output cardiac failure coma

Complications Treatment of a thyroid storm: B-blocker (propranolol) Propylthiouracil (PTU) Iodine Cooling measures

Toxic Adenoma Treatment Radioiodine Surgery  Preferred for children and adolescents  Preferred for very large nodules when high I131 doses needed