Thyroid Gland

- The first endocrine gland to develop. - Endodermal origin. - Originates from the ventral embryologic digestive tract. - midline diverticulum (foramen cecum of tongue) – 4 th week → descends as median thyroid component → week → descends as median thyroid component → ISTHMUS ISTHMUS - True histological differentiation week.

Thyroid Gland - The lateral Thyroid component develops on each side from the caudal pharyngeal endoderm. - Arises latter than the Medial. - Fuse with the posterior portion of the median component on each side → C Cell migration from the neural crest. - Basic Glandular Function begins at the 3 month of Gestation.

Thyroid Gland - Functional Disorders: Hyper Thyroidism: - Grave ’ s dibease - Grave ’ s dibease - Toxic Multinodular Goiter - Toxic Multinodular Goiter - Solitary Toxic Adenoma - Solitary Toxic AdenomaHypothyroidism Thyroiditis: - Hashimoto Thyroiditis - Painelss or Postpartum Thyroiditis - Painelss or Postpartum Thyroiditis - Subactue Thyroiditis - Subactue Thyroiditis - Amiodarone Induced Thyroiditis or - Amiodarone Induced Thyroiditis or Thyrotoxicosis. Thyrotoxicosis. - Acute Thyroiditis - Acute Thyroiditis - Riedel ’ s Thyroiditis - Riedel ’ s Thyroiditis

Thyroid Gland Nodular Thyroid disease - Nontoxic Multinodular Goiter - Solitary or Dominant Thyroid Nodule.

Thyroid Gland Malignancy - Incidence 4/ population / year. - Wide spectrum of behavior. - 98% of Thyroid cancer are well differentiated. - More or less same surgical approach.

Thyroid Gland Malignancy IPapillary Carcinoma – 80% - Follicular variant - Microcarcinoma IIFollicular Carcinoma – 10-20% - Minimally Invasive IIIHurtel Cell Carcinoma – 5% IVMedullary Carcinoma – 7% Parafollicular C Cells Parafollicular C Cells VAnaplastic Carcinoma – 1-2% VIThyroid Lymphoma - < 5% - non Hodgkin (B cell origin) - usually arise from Hashimoto Thyroiditis

Thyroid Gland Treatment of Malignancy - Surgery - Radioiodine Therapy - External Beam Radiotherapy - TSH Suppression

Thyroid Gland Complication of Surgery 1. Bleeding 2. Airway Obstruction 3. RLN Injury 4. Hypoparathyroidism 5. Injury EBSLN

Parathyroid Gland 4 glands: 2 superior (LT+RT) 2 inferior LT + RT 2 inferior LT + RT - 5-7mm x 0.5-2mm mg - Superior glands: - post surface of thyroid gland were RLN pierces the larynx were RLN pierces the larynx - No variation - No variation Inferior glands: - Variable  The surgeon must have a thorough understanding of the anatomic variations. understanding of the anatomic variations.

Parathyroid Gland Anatomy 4-5 th week -> 4 pharyngeal pouches 4 th → Sup parathyroid + Lat thyroid Remain in close association with the upper pole of the Thyroid. Thyroid. 3 rd → Inf parathyroid – Descends with the Thymus 3 rd → Inf parathyroid – Descends with the Thymus Extremely variable migration Extremely variable migration - Supernumerary: 6 -15% - Intrathyroid parathyroid – rare

Parathyroid Gland Physiology - Calcium - Phosphate - Regulation: - GI tract - Skeleton - Skeleton - Kidneys - Kidneys - PTH - PTH - Vit D - Vit D - Calcitonin - Calcitonin

Parathyroid Gland Hyperparathyroidism - Primary Hyperparathyroidism:Adenoma – 80% Double Adenoma – 6% Hyperplasia – 12-14% - Secondary Hyperparathyroidism - Tertiary Hyperparathyroidism - Parathyroid Carcinoma

Primary Hyperparathyroidism Laboratory Findings Serum Urine - Ca -  Ca / 24h - P -  P / 24h - PTH - Tubular reabsorption of P < 30% reabsorption of P < 30% - Mg (5-10%) - Bicarbonate  Hyperchloremic Metabolic Acidosis Hyperchloremic Metabolic Acidosis A ratio > 30 cl/p = Hyperparathyroidism. A ratio > 30 cl/p = Hyperparathyroidism.

Primary Hyperparathyroidism Localization - U.S - 99m technetium sestamibi scintigraphy - CT - MRI - Versus Sampling

Parathyroid Gland Indication for Surgery* - Elevated serum calcium (>1mg/dL above normal) - History of an episode of life – threatening Hypercalcemia -  Createnin clearance - Kidney stones - Markedly  24h calcium excretion - Substantially  bone mass (Tscore < - 2.5) * NIH Consensus

Parathyroid Gland Surgery - Bilateral Neck Exploration. - Unilateral Neck Exploration. - Minimally Invasive Parathyroidectomy. - Total Parathyroidectomy  Auto transplantation.