THE THYROID GLAND

Anatomy :

The throid is in the superficial anterior neck Is bilobed, with a connecting isthmus. The shape Is often described as that of the H of the Honda car symbol.Neoplastic or hyperplastic growth may extend inferiorly (retrosternal), The adjacent anatomy of the laryngeal nerves and parathyroid glands is an important surgical consideration.In adults it wheighs approximately 10-20 gram. The thyroid gland has a rich blood suppy

Iodine metabolism

Iodine enters the body in food or water

The thyroid gland concentrates and traps iothyroglobulin, which compensates for the scarcity of iodine.

Most of the dietary iodide is excreted in the urine,

a 24-hour urinary iodide concentration is

excellent index of dietary intake.

Control of thyroid function

(1) The classic hypothalamic- pituitary-thyroid axis, (2) The pituitary and peripheral deiodinases, modify the effects of T4 and T3; (3) Autoregulation of hormone synthesis by the thyroid gland (4) Stimulation or inhibition by TSH receptor autoantibodies.

The syntheis of T4 and T3 by the thyroid gland involves six major steps;

active transport of I- across the basement membrane into the thyroid cell (trapping of iodide); oxidation of iodide and iodination of tyrosyl residues in thyroglobulin; coupling of iodotyrosine molecules within thyroglobulin, to form T3 and T4proteolysis of thyroglobulin, free iodothyronines and iodotyrosines; deiodination of iodotyrosines within the thyroid cell, conservation, reuse of the liberated iodide;under certain circumstances,intrathyroidal 5-deiodination of T4 to T3.

Effects of TSH on the Thyroid cell

Changes in thyroid cell morphologyCell growthIodine metabolism TSH stimulates all phases of iodide metabolism, Other effect of TSH increased secretion of T4 and T3 from the gland.

increased activity of type 1 5-deiodinase, conserving intrathyroidal iodine.

Stimulation of glucose uptake, oxygen consumption,

The serum level of TSH is about 0.5-5 mU/L;it is increased in hypothyroidism and decreased in hyperthyroidism

If iodide intake is below 50 g/d,

unable to maintain adequate hormonal secretion,

thyroid hypertrophy (goiter) hypothyroidism

Effect of Iodide Deficiency on Hormone Biosynthesis

A diet very low in iodine reduces intrathyroidal iodine content

increases the intrathyroidal ratio of MIT to TIT-

increases the ratio of T3 to T4 ---

decreases the secreation of T4,-

increases serum TSH.

Struma

DISORDERS OF THE THYROID

Patients with thyroid disease will usually complain of

thyroid enlargement, diffuse or nodular; symptoms of thyroid deficiency ( hypothyroidism) symptoms of thyroid hormone excess ( hyperthyroidism) or complications of a specific form of hyperthyroidism e.g Graves disease * prominence of the eyes (exophthalmos) and,* thyroid dermopathy

Hyperthyroidism & thyrotoxicosis

Thyrotoxicosis = clinical syndrome that results when tissues are exposed to high levels of circulating thyroid hormone

due to hyperactivity of the thyroid gland, hyperthyroidism

Conditions associated with thyrotoxicosis

Diffuse toxic goiter (Graves disease)Toxic adenoma (Plummers disease)Toxic multinodular goiterSubacuta; thyroiditisHyperthyroid phase of Hashimotos thyroiditisThyrotoxicosis factitia

Diffuse Toxic Goiter (Graves Disease)

females > males (5) : (1) between 20-40 years of age.

Consists of one or more of the following features :

(1) thyrotoxicosis, (2) diffuse goiter, (3) ophthalmopathy (exophthalmos), and(4) dermopathy (pretibial myxedema).

Clinical Features

A. Symptoms * palpitations, * nervousness, * easy fatigability, * hyperkinesia, * diarrhea, * excessive sweating, * intolerance to heat, * preference for cold. * marked weight loss without loss of appetite

* thyroid enlargement, * thyrotoxic eye signs tachycardia skin : smooth, moist and warm fine tremor of the fingers* muscle weakness and * loss of muscle mass ( myopathy)* atrial fibrillation insensitive to digoxinB. Signs

INDEKS WAYNEGejala yang baru terjadiDan bertambah beratTanda-tanda+-+-Sesak pada kerjaBerdebar-debarLekas lelahLebih suka hawa panasLebih suka dinginBerkeringat banyakGugupNafsu makan bertambahNafsu makan berkurangBerat badan bertambah+1+2+3- 5+5+3+2+3- 3- 3----------Tiroid terabaBising pembuluhEksopthalmusRetraksi palpebraKelambatan palpebraHiperkinesisTremor jariTangan panasTangan lembabDenyut nadi sewaktu< 80 / menit80-90 / menit> 90 / menitFibrilasi atrium+3+2+2+2+1+4+1+2+1

-3-+3+4-3-2----2--1-1

----JumlahNilai : 19 : toksik, 11 19 : Equivocal, < 11 : non toksik

Laboratory FindingsHigh FT4 + suppressed TSH (< 0,1 uU/L) hyperthyroidism. +eye signs diagnosis of Graves disease can be made without further tests.

Thyroid imaging

Radiounclide Imaging* both the size and shape of the thyroid gland * distribution of functional activity in the gland. Cold, warm and hot thyroid nodules

Thyroid ultrasonography or- measuring the size of the gland or individual nodules - differentiating solid from cystic lesions

MRI (magnetic resonance imaging)- excellent image of the thyroid gland, - including posterior or substernal extention

Thyroid biopsyFine-nndle aspiration biopsy. Effect of thyroid hormone in peripheral tissue basal metabolic rate (BMR). hypereflexion

Treatment of Graves Disease

Management has been largely directed toward controllingthe hyperthyroidism.

Blocking of hormone synthesis by antithyroid drug therapy, Partial ablation of the thyroid gland by surgery, and Destruction of thyroid cells by radioactive iodine therapy.

HYPOTHYROIDISM

Signs and Symptoms are the reverse of thyrotoxicosis