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Dr Malith Kumarasinghe MBBS (Colombo)

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Hormones Transmit information between cells or organs Allow adjustment of internal and external environment Endocrine organs Synthesis and release hormones Maintain homeostatic mechanisms

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Endocrine Disorders Caused by abnormalities in hormone Synthesis Secretion Control Function

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Common Endocrine Disorders Diabetes mellitus Thyroid Disease Subfertility Menstrual disorders Osteoporosis Short Stature Delayed puberty

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Thyroid Disorders

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Surface Anatomy of Thyroid

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Where to look for Thyroid ?

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Background What: brownish-red, highly vascular gland Location: ant neck at C5-T1, overlays 2 nd 4 th tracheal rings Avg width: 12-15 mm (each lobe) Avg height: 50-60 mm long Avg weight: 25-30 g in adults (slightly more in women) **enlarges during menstruation and pregnancy**

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Thyroid is made up of The isthmus The lateral lobes An inconstant pyramidal lobe projecting from isthmus

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Relations Anterior Pretracheal fascia Strap muscles Sternocleidomastoid Anterior jugular vein

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Posterior Larynx and Trachea Pharynx and oesophagus Carotid sheath

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Blood Supply Arterial Superior thyroid artery Inferior thyroid artery Thyroid ima artery

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Venous Superior thyroid vein Middle thyroid vein Inferior thyroid vein

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Innervation Principally from Autonomic Nervous system Parasympathetic fibers from vagus Sympathetic fibers from superior, middle, and inferior ganglia of the sympathetic trunk Enter the gland along with the blood vessels.

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Recurrent laryngeal nerve important structure lying between trachea and thyroid may be injured during thyroid surgery ipsilateral vocal cord paralysis, hoarse voice

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Questions Components of the thyroid gland? Relations of the thyroid gland?

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Physiology

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Produces hormones thyroxine (T 4 ) and tri-iodothyronine (T 3 ) are dependent on iodine and regulate basal metabolic rate calcitonin which has a role in regulating blood calcium levels

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O OH I I I I O NH 2 Thyroxine (T 4 ) O OH I I I O NH 2 3,5,3-Triiodothyronine (T 3 ) THYROID HORMONES

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Thyroid hormones structure Thyroid hormones stored conjugated to thyroglobulin, but are cleaved by pinocytosis before being released into circulation Majority of the thyroid hormone secreted is T 4 (90%), but T 3 is the considerably more active hormone Although some T 3 is also secreted, most is derived by deiodination of T 4 in peripheral tissues, especially liver and kidney Both are poorly water soluble 99% of circulating thyroid hormone is bound to carrier protein (mostly thyroxine-binding globulin, but also transthyrein and albumin)

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Thyroid hormones function Likely that all cells express thyroid hormone receptors Metabolism Increases basal metabolic rate Increases carbohydrate and lipid metabolism Normal growth Normal development Especially CNS Other systems CVS increases heart rate, cardiac output CNS mental acuity Reproduction fertility requires normal thyroid function

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Thyroid regulation

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www.medscape.comwww.medscape.com; http://ae.medseek.com/http://ae.medseek.com/

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Thyroid pathology Normal thyroid function - euthyroidism Disease states may result in hyper- or hypo- thyroidism - relative excess or deficiency of thyroid hormones Any swelling of the thyroid may be termed a goitre Toxic goitre: associated with increased thyroid hormone output Non-toxic goitre: normal hormone levels (Non-specific terms; dont relate to a particular pathology)

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Epidemiology http://www.scielosp.org/scielo.php

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Hyperthyroidism

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Prevalence Women 2% Men 0.2% 15% of cases occur in patients older than 60 years of age

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Causes of Hyperthyroidism 1. Graves Disease Diffuse Toxic Goiter 2. Plummers Disease 3. Toxic phase of Sub Acute Thyroiditis 4. Toxic Single Adenoma 5. Pituitary Tumours excess TSH 6. Molar pregnancy & Choriocarcinoma ( HCG) 7. Metastatic thyroid cancers (functioning) 8. Struma Ovarii (Dermoid and Ovarian tumours)

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Graves Disease The most common cause of thyrotoxicosis (50- 60%). Organ specific auto-immune disease The most important autoantibody is Thyroid Stimulating Immunoglobulin (TSI) TSI acts as proxy to TSH and stimulates T 4 and T 3

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Toxic Multinodular Goiter (TMG) TMG is the next most common hyperthyroidism - 20% More common in elderly individuals long standing goiter Lumpy bumpy thyroid gland Milder manifestations (apathetic hyperthyroidism) Mild elevation of FT 4 and FT 3 Progresses slowly over time Clinically multiple firm nodules (called Plummers disease)

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Other causes.. Sub Acute Thyroiditis (SAT) Toxic Single Adenoma (TSA)

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Common Symptoms 1. Nervousness 2. Anxiety 3. Increased sweating 4. Heat intolerance 5. Tremor 6. Hyperactivity 7. Palpitations 8. Weight loss despite increased appetite 9. Reduction in menstrual flow or oligo- menorrhea

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Common Signs 1. Hyperactivity, Hyper kinesis 2. Sinus tachycardia or atrial arrhythmia, AF, CHF 3. Systolic hypertension, wide pulse pressure 4. Warm, moist, soft and smooth skin- warm handshake 5. Excessive perspiration, palmar erythema, Onycholysis 6. Lid lag and stare (sympathetic over activity) 7. Fine tremor of out stretched hands format's sign 8. Large muscle weakness, Diarrhea, Gynecomastia

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Proptosis Lid lag Thyroid Ophthalmopathy

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Onycholysis

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Acute, severe, exacerbation of thyrotoxicosis due to acute serum T 3 /T 4. Causes: stressors DKA, infection, acute I - tx withdrawal, trauma, thyroid gland manipulation, radioactive I -, surgery, ether anesthesia. Onset: sudden. For surgical pts at risk, it may occur: Intraop Postop: 6-18hrs. Signs T, HR, CHF, confusion, shock, death. Thyroid storm

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Diagnosis 1. Typical clinical presentation 2. Markedly suppressed TSH (