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211

Most Common cause of Primary Hypothyroidism

Iodine deficiency

212

– Auto-immune disease presenting with increased
lymphocytes and macrophages destroying the
thyroid
– Anti-Thyroglobulin, Anti-Microsomal antibodies

Hashimoto’s Thyroiditis

213

(Bone)
– Ground Substances
• ECF + Chondroitin Sulfate + Hyaluronic Acid
• Gelatinous medium
– Collagen Fibers
• 95% of Organic Matrix
• for TENSILE STRENGTH

ORGANIC MATRIX

214

(Bone)
– Ca10(PO4)6(OH)2
– for COMPRESSIONAL STRENGTH

BONE SALTS

215

Continuous in response to bone stress

Bone Remodeling

216

Osteoblast - Secrete Collagen & Ground Substance where calcium precipitates

BONE DEPOSITION

217

Osteoclasts - Secrete Lysosomal enzymes, Citric Acid and
Lactic Acid

BONE ABSORPTION

218

– 99% as hydroxyapatite in Bone
– 0.1% in the interstitium

BODY CALCIUM

219

Calcium Metabolism

Positive calcium balance
– Calcium Intake > Calcium Excretion

Negative calcium balance
– Calcium Intake

220

Effect of PTH

Intestine: Indirectly INCREASES CALCIUM and PHOSPHATE absorption by inc. vitamin D metabolite

Kidney: DECREASE CALCIUM excretion and INCREASED PHOSPHATE excretion

Bone: CALCIUM and PHOSPHATE RESORPTION INCREASED by continuous high concentrations. Low intermittent doses increase bone formation

221

Net Effect of PTH on Serum Levels

Serum Calcium increased, Serum phosphate decreased

222

Effect of Active Vitamin D metabolite

Intestine: INCREASED CALCIUM AND PHOSPHATE absorption

Kidney: Increased resorption of Phosphate. Loss of CALCIUM in the urine

Bone: Direct effect - INCREASED CALCIUM and PHOSPHATE resorption
Indirect effect - promoting MINERALIZATION by INCREASING THE AVAILABILITY OF CALCIUM AND PHOSPHATE

223

Net Effect of Active Vitamin D metabolite on Serum Levels

BOTH INCREASED in serum CALCIUM and PHOSPHATE

224

Vitamin D Synthesis

Vitamin D comes from Cholesterol
1. Starts at the Skin: Calciol (Cholecalciferol)
2. 1st activation: Liver Calcidiol (25 hydroxyCholecalciferol)
3. 2nd activation: Kidney Calcitriol (1,25 dihydroxyCholecalciferol)

225

Secreted by the Parafollicular cells of the Thyroid

Decreases plasma calcium concentration
– Decreases number and activity of osteoclast
– Effects in Children > Adults

Calcitonin

226

Effects on Parathyroid Hormone Secretion:

– Magnesium effect on PTH is similar to calcium
o Hypomagnesemia stimulates PTH secretion
– Increased phosphate forms calcium phosphate which reduces stimulation of Ca-sensitive receptors which trigger an increase in PTH

227

- Hypercalcemia
- Hypophosphatemia
- Osteitis Fibrosa Cystica – Due to great osteoclastic activity
- Increases Alkaline Phosphatase – Secreted by osteoblast in an attempt to neutralize osteoclast activity

HYPERPARATHYROIDISM

228

Primary Hyperparathyroidism Effect on Serum and Urine

SERUM
Calcium: Increased
Phosphorus: Decreased
Alkaline Phosphatase: Increased or None

URINE
Calcium: Increased
Phosphorus: Increased

229

Secondary Hyperparathyroidism Effect on Serum and Urine

SERUM
Calcium: None or Decreased
Phosphorus: Increased
Alkaline Phosphatase: Increased or None

URINE
Calcium: Decreased
Phosphorus: Decreased

230

Hypocalcemia: interferes with normal muscle contraction and nerve conduction
– Paresthesias
– Tetany and Seizures
– Possible laryngeal spasm
– Fatigue, headaches, bone pain and insomnia, crampy abdominal pain
– Chvostek’s sign

HYPOPARATHYROIDISM

231

– secretes pancreatic juice to duodenum

Acini

232

- secretes insulin and glucagon directly into the blood.

Islets of Langerhans

233

▪ 60% of islet cells
▪ Lies in the middle of each islet
▪ Secretes insulin and amylin

Beta cells

234

▪ 25% of islet cells
▪ Secretes glucagon

Alpha cells

235

▪ Around 10% of total
▪ Secretes Somatostatin

Delta cells

236

▪ Minority in islet cells
▪ Secrets pancreatic polypeptide – uncertain function

PP cells

237

▪ Small protein with MW 5,808
▪ Composed of two amino acid chains linked with 2 disulfide bridges
▪ Starts as insulin preprophormone from RER of beta cells resulting to proinsulin

INSULIN

238

are cleaved in golgi apparatus insulin and peptide fragments (proinsulin has no intrinsic activity)

Proinsulin