Parathyroid/Thyroid Metabolic Bone Disease
Osteodystrophy
Definition: Defective formation of bone
Causes
Renal osteodystrophy
Alteration of bone morphology in pts with CKD
Skeletal change secondary to chronic renal disease, increased osteoclastic bone resorption, and osteomalacia/sclerosis/porosis
Pathophyysiology
Renal failure leads to retention of phosphates
Increased phosphates (hyperphosphatemia) leads to hypocalcemia since phosphate precipitates with calcium and inability to convert vitamin D to active form
Leads to oversecretion of PTH
Leads to increase bone resoprion
Pagets Disease
Disease that leads to excessive bone resorption which results in lytic lesions
Pathophysiology
Localized increase in osteoclast formation that leads to bone resorption
Stages
1: Osteoclastic Resoprtive stage: Lots of osteoclasts
- Osteoblastic and osteoclastive activity stage: Disordered woven bone formation, deposited in tile-like or mosaic pattern
- Burnt out stage: Bone sclerosis composed of mosaic pattern of lamellar bone with thickened trabeculae and cortices
Clinical Features
Fractuyres, osteoarthriits, skeletal deformities, tibila bowing
Hyperparathyroidism
Caused by increase production of parahthyroid hormone
Types
Priamary (hyperplasia or tumour)
Secondary Prolonged hypocalcemia resulting in compsation of PTH
Teritiary: Autonomous production of PTh in patients wiht CRF
Leads to increased osteoclasts, increased tunneling, and increased amounts of woven bone production
Thyroid Cancer
Thyroid Nodules
Hot or cold, solitary or multiple, male child, entire lobe or both lobes, older male
Clinical Features
Benign neoplasms outnumber canrcinomas, more likely to be female,
Papillary thyuroid carcinoma
Characteristics
Most common thyroid amlignancy
Risk Factors
Ionizing radiation, iodine rich diet, previous benign thyroid disease
Features
Vascualr or capsular invasion, variable growth, elongated follicles, psammonma bodies, fiborsis, colloid and scalloping, crystals or giant cells
Cytologic
Enlarged cells, high nuclear to cytoplasmic ratio, nuclear overlapping, crowding, irregular placement around follicle
Follicular Adenoma
Benign neoplastic nodule with complete capsule, no invasion, or metastases
Small follicles, lacks nuclear features, and may show papillary hyperplasia
Follicular carcinoma
Malignant tumour composed of follicular cells
Need to examine entire capsule to rule out follicular carcinoma
Anaplastic thyroid carcinoma
Composed of mostly large pleomorphic and spindled cells
Medullary thyroid carcinoma
Polygonal to spindle-shaped cells arranged in nests, ribbons, and follicles
Amyloid deposits, and foci of C-cell hyperplasia
Common Thyroid Disorders
Hashimottos
Large infiltration of lymphocytes, plasma cells, macrophages and lymphoid follicles inside thyroid
Graves Disease
Diffuse papillary hyperplasia, back to back follicles, scant or absent colloid
Diffuse Goiter
Enlartged follicles filled with colloid
Multinodular goiter
Recurrent episodes of stimulation and involution of a diffuse goiter
Most long-standing simple goiters convert to MNGs