Endocrinology Dr Malith Kumarasinghe MBBS (Colombo)
Hormones Transmit information between cells or organs Allow adjustment of internal and external environment Endocrine organs Synthesis and release hormones Maintain homeostatic mechanisms
Endocrine Disorders • Caused by abnormalities in hormone Synthesis Secretion Control Function
Common Endocrine Disorders • Diabetes mellitus • Thyroid Disease • Subfertility • Menstrual disorders • Osteoporosis • Short Stature • Delayed puberty
Background • What: brownish-red, highly vascular gland • Location: ant neck at C5-T1, overlays 2nd – 4th 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**
Thyroid is made up of • Theisthmus • Thelateral lobes • An inconstant pyramidal lobe projecting from isthmus
Relations • Anterior Pretracheal fascia S trap muscles Sternocleidomastoid Anterior jugular vein
Posterior Larynx and Trachea Pharynx and oesophagus Carotid sheath
Blood Supply • Arterial Superior thyroid artery Inferior thyroid artery Thyroid ima artery
Venous Superior thyroid vein Middle thyroid vein Inferior thyroid vein
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.
Recurrent laryngeal nerve important structure lying between trachea and thyroid • may be injured during thyroid surgery ipsilateral vocal cord paralysis, hoarse voice
Questions • Components of the thyroid gland? • Relations of the thyroid gland?
Produces hormones • thyroxine (T4) and tri-iodothyronine (T3) are dependent on iodine and regulate basal metabolic rate • calcitonin which has a role in regulating blood calcium levels
OH OH I I I I I O O NH2 NH2 I I OH OH O O 3,5,3’-Triiodothyronine (T3) THYROID HORMONES Thyroxine (T4)
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 T4 (90%), but T3 is the considerably more active hormone • Although some T3 is also secreted, most is derived by deiodination of T4 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 transthyreinand albumin)
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
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; don’t relate to a particular pathology)
HYPERTHYROIDISM Prevalence Women 2% Men 0.2% 15% of cases occur in patients older than 60 years of age
Causes of Hyperthyroidism • Graves Disease – Diffuse Toxic Goiter • Plummer’s Disease • Toxic phase of Sub Acute Thyroiditis • Toxic Single Adenoma • Pituitary Tumours – excess TSH • Molar pregnancy & Choriocarcinoma (↑↑ βHCG) • Metastatic thyroid cancers (functioning) • Struma Ovarii (Dermoid and Ovarian tumours)
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 T4 and T3
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 FT4 and FT3 • Progresses slowly over time • Clinically multiple firm nodules (called Plummer’s disease)
Other causes….. • Sub Acute Thyroiditis (SAT) • Toxic Single Adenoma (TSA)
Common Symptoms • Nervousness • Anxiety • Increased sweating • Heat intolerance • Tremor • Hyperactivity • Palpitations • Weight loss despite increased appetite • Reduction in menstrual flow or oligo-menorrhea
Common Signs • Hyperactivity, Hyper kinesis • Sinus tachycardia or atrial arrhythmia, AF, CHF • Systolic hypertension, wide pulse pressure • Warm, moist, soft and smooth skin- warm handshake • Excessive perspiration, palmar erythema, Onycholysis • Lid lag and stare (sympathetic over activity) • Fine tremor of out stretched hands – format's sign • Large muscle weakness, Diarrhea, Gynecomastia
Thyroid Ophthalmopathy Proptosis Lid lag
Thyroid storm • Acute, severe, exacerbation of thyrotoxicosis due to acute serum T3/T4. • 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.
Diagnosis • Typical clinical presentation • Markedly suppressed TSH (<0.05 µIU/mL) • Elevated FT4 and FT3 (Markedly in Graves) • Thyroid antibodies – by Elisa – anti-TPO, TSI • ECG to demonstrate cardiac manifestations • Nuclear Scintigraphy to differentiate the causes
Treatment Options • Symptom relief medications • Anti Thyroid Drugs – ATD • Methimazole, Carbimazole • Propylthiouracil (PTU) • Radio Active Iodine treatment – RAI Rx. • Thyroidectomy – Subtotal or Total • NSAIDs and Corticosteroids – for Sub acute thyroditis
Dietary Advice • Avoid Iodized salt, Sea foods • Excess amounts of iodide in some • Expectorants, x-ray contrast dyes, • Seaweed tablets, and health food supplements These should be avoided because the iodide interferes with or complicates the management of both ATD and RAI Rx.
1.8% of total population. • Second only to DM as most common endocrine disorder. • Incidence increases with age. • More common in females. • 2-3% of older women.
Etiology PRIMARY HYPOTHYROIDISM • Hoshimoto’s thyroiditis-most common • Idiopathic hypothyroidism-probably old Hoshimoto’s • Irradiation of thyroid • Surgical removal • Late stage invasive fibrous thyroiditis • Iodine deficiency • Drug therapy (Lithium, Interferon)
SECONDARY HYPOTHYROIDISM • 5% of cases. • Pituitary or hypothalmic neoplasm. • Congenital hypopituitarism. • Pituitary necrosis (Sheehan’s syndrome)
Thyroid Failure - Organ Systems Cardiovascular • Decreased ventricular contractility • Increased diastolic blood pressure • Decreased heart rate Central Nervous • Decreased concentration • General lack of interest • Depression Gastro-instestinal • Decreased GI motility • Constipation www.drsarma.in
Thyroid Failure - Organ Systems • Musculoskeletal • Muscle stiffness, cramps, pain, weakness, myalgia • Slow muscle-stretch reflexes, muscle enlargement, atrophy Renal • Fluid retention and oedema • Decreased glomerular filtration www.drsarma.in
Thyroid Failure - Organ Systems Reproductive • Arrest of pubertal development • Reduced growth velocity • Menorrhagia, Amenorrhea • Anovulation, Infertility Hepatic • Increased LDL / TC • Elevated LDL + triglycerides www.drsarma.in