• Largest endocrine gland • Devoted only to endocrine function • Oldest gland phylogenically – All vertebrates, many invertebrates
•T4 and T3: Same in all vertebrates from land mammals to teleosts • TSH: Trophic and secretion • Each tissue regulates its thyroid status • Important for metamorphosis and development – Amphibian and frog metamorphosis – Eye opening in rats (day 10) – CNS development in mammals (cretins)
NIS IHC: 2 mo. old Mouse
Berlin 2017 Thomas Rosol 1 Endocytosis of Colloid NIS IHC: 9 mo. old Mouse
Thyroid Hormone Deiodination Activation and Metabolism Thyroid Hormone Deiodination
3’ 3 • Deiodinase I (liver, kidney) – T4 to T3 or rT3 to T2 * 5’ 5 • (5’)-Deiodinase II (thyroid, heart, CNS, fat, 3,5,3’,5’-T4 muscle) – Deiodinates the outer ring only – Major activating enzyme 3,5,3’-T 3 3,3’,5’-rT 3 – T4 to T3; rT3 to T2 • Deiodinase III (fetus, placenta) – T4 to rT3; T3 to T2 3,3’T2
Berlin 2017 Thomas Rosol 2 Thyroid Stimulating Hormone Short Term Response of Follicular Cells (TSH) To Increased TSH Secretion • Glycoprotein: Alpha & Beta subunits • Short (~15 minute) half-life • Circulates free (unbound) in blood • Highly species-specific – Human, primate, rat, & dog assays – Little cross reactivity – Male rats greater than females
Long Term Response of Follicular Cells Replacement Therapy with Thyroxine To Increased TSH Secretion
• Ventral Midline • Base of Tongue to Anterior Mediastinum • Thyroidogenic Epithelium in Wall • Colloid-Like Contents
Berlin 2017 Thomas Rosol 3 Ultimobranchial Duct Cysts
Cysts occur at the thyroid hilus; have a squamous epithelial lining; and accumulate keratin.
Thyroid: Fetal Hypoplasia Guernsey, prolonged gestation Pathology of the Thyroid Gland
Berlin 2017 Thomas Rosol 4 Ectopic Thyroid Parenchyma Ectopic Thyroid: Dog
• Base of tongue to diaphragm • Species: Dog • Humans (10%) • Location – Usually sublingual, rare intracardiac – Along course of thyroglossal duct in cervical • Dogs (50%) region (>100%) – Intrapericardium, heart base – Intrathoracic (~50%) • Anterior mediastinum – Intracardiac; septum and right ventricle • Pericardium • Neoplasia more easily identifiable • Adventitia of the aorta • Primates (rare) • Significance • Rats and mice (rare) – Thyroidectomy is difficult – Neck, thorax, heart base – Can undergo hyperplasia or neoplasia
Persistence of Thyroid Remnants at Base of Tongue (Foramen Caecum)
Significance:
Cysts Neoplasms
Berlin 2017 Thomas Rosol 5 Lipofuscin Pigment
• Accumulates in thyroid follicular cells with advancing age • Age-related color change to the thyroid gland – Young animals: Red – Aged animals: Dark brown
THYROID ATROPHY
• Trophic Atrophy – Subnormal TSH Production • Pituitary Neoplasm • Space-Occupying Cyst or Granuloma
• Pressure Atrophy – Bilateral Lesions Adjacent to Thyroid • Cervical Cyst • Abscess • Neoplasm
Berlin 2017 Thomas Rosol 6 Colloid Involution COMMON CAUSES Thyroid Gland HYPOTHYROIDISM IN DOGS
• Atrophy of Follicular Cells – Low Cuboidal • LYMPHOCYTIC • FOLLICULAR THYROIDITIS ATROPHY • Decreased TSH-Mediated Endocytosis of Colloid Immune-Mediated Idiopathic • Distention of Follicles with Colloid ~50% ~50% – Macrofollicles
DDx: Sick Euthyroid Syndrome
Sick Euthyroid Syndrome
• Overdiagnosis of hypothyroidism in critical illness
• Decreased conversion of T4 to T3
–↓ T3 and ↑ reverse T3
– Normal or ↓ T4 – Normal or ↓ TSH • Changes in binding of thyroid hormones to serum proteins
TSH IRMA for Dogs
•TSH: subunits are unique • TSH levels are low in dogs compared to humans • False negative rate – up to one third • False positive rate – 10-20 percent • Combine with ultrasonography • Alternative: TSH stimulation test – Bovine pituitary extract (Sigma) not available due to Mad Cow Disease and development of human recombinant TSH (Thyrogen, Genzyme)
Berlin 2017 Thomas Rosol 7 IDIOPATHIC THYROID ATROPHY “FOLLICULAR COLLAPSE”
• Noninflammatory • Adipose Connective Degenerative Lesion Tissue Replacement
Berlin 2017 Thomas Rosol 8 LYMPHOCYTIC THYROIDITIS (HASHIMOTO’S)
• Species – Dog, chicken, laboratory rats – Non-human primates – Human beings
• Thyroid antigens – Thyroglobulin – Thyroperoxidase (microsomal) – TSH receptor protein – Secondary antigens: colloid, nuclear, cytoskeletal proteins, tubulin
IMMUNE-MEDIATED THYROIDITIS
• Humoral immune response – Autoantibody production – Immune complexes along basement membrane – Proliferation of b-lymphocytes in thyroid
• Cell-mediated immune response – Sensitized t-lymphocytes – Antibody-dependent cytotoxicity – Defective suppressor t-lymphocytes
LYMYPHOCYTIC THYROIDITIS
• ‘End stage’
• Interstitial fibrosis
• Loss of thyroid follicles
• Prominent C cells
• Oncocytes (acidophilic cells with numerous mitochondria)
Berlin 2017 Thomas Rosol 9 Hypothyroidism: Other Lesions Myxedema
Immune-Mediated Diseases of the Endocrine System
• Lymphocytic Thyroiditis (Hashimoto’s) • Lymphocytic Adrenalitis (Addison’s) • Lymphocytic Parathyroiditis • Juvenile-onset Diabetes Mellitus • Hypothalamic Diabetes Insipidus
Berlin 2017 Thomas Rosol 10 Radiation-Induced Thyroiditis (131I, 125I)
• Degeneration of Follicular Cells
• Disruption of Thyroid Follicles
• Thyroiditis
SOURCES OF THYROID 131I Therapy in Cats RADIATION EXPOSURE
TYPE SOURCE • Necrosis of parenchymal cells -Treatment of HyperTG with 131I INTENTIONAL -Diagnostic Scanning with 131I • Vascular damage or 123I – Thrombosis; hemorrhage
-Radiotherapy of head and • Healing by fibrosis and collagen INADVERTANT neck cancer deposition -Atomic bomb blasts (Japan) • Loss of stem cells -Fallout (131I) from testing nuclear weapons -Laboratory Accidents ACCIDENTAL -Nuclear Reactor Accidents
Histopathology Histopathology
Berlin 2017 Thomas Rosol 11 IONIZING RADIATION
ONLY KNOWN THYROID CARCINOGEN IN HUMANS
THYROID CANCER IN CHILDREN
CHERNOBYL NUCLEAR REACTOR ACCIDENT
THYROID CARCINOMAS REPRESENT THE LARGEST NUMBER OF CANCERS OF ONE TYPE, CAUSED BY A SINGLE EVENT, ON ONE DATE, EVER RECORDED
Reasons for High Incidence of Thyroid Cancer after Chernobyl Nuclear Reactor Accident
• Greater Thyroid Exposure to Fallout Radioiodine – Milk is main route for Ingestion of Radioiodine • Intake: Children > Adults • Goat’s Milk has 10X more Iodine than Cow’s Milk – Uptake of Iodine is higher in Children • Thyroid Growth Occurs Primarily in Childhood – Sleeping Outdoors Increases Exposure
Berlin 2017 Thomas Rosol 12 Goiter
Hypertrophy and Hyperplasia of Follicular cells
-Nonneoplastic -Noninflammatory
Goiter Goiter
• Ancient disease – Described for over 5000 years • Major human health problem • Historical interpretation • Predominantly due to iodine deficiency – Sign of beauty • Estimated over 200 million people affected – Punishment of gods – Adults • Iodine deficient regions – E.g., Great Lakes in USA
Goiter: Causes
• Deficient iodine intake – Deficient areas of the world – Mountainous regions; recent glaciation • Genetic enzyme defects – Congenital dyshormonogenetic goiter • Increased thyroxine demand
Berlin 2017 Thomas Rosol 13 Goiter: Causes Amphibian Metamorphosis Assay
• Goitrogenic chemicals • Detect substances that interact with – Block iodide trapping; NaI symporter hypothalamic-pituitary-axis during development – Conserved thyroid structure in vertebrates – Inhibit thyroperoxidase (TPO) with failure to oxidize iodide (I-) to I • Metamorphosis of Xenopus Laevis (African 2 Clawed Frog) tadpoles – Failure of fusion of colloid droplet and lysosomal bodies resulting in a failure to • Test for Endocrine Active Substances (EAS)
release T4 and T3 • OECD (Org. Economic Co-operation & Development guidelines (www.oecd.org/dataoecd/44/52/40909207.pdf)
Nieuwkoop and Faber (N&F) Stages • 21-day test – Hind limb length, development stage, thyroid histology • Nieuwkoop and Faber (N&F) staging – 45-49: First form tadpole – 49-56: Second form tadpole – 56-60+: Third form tadpole
Control Perchlorate (62 ug/L) Diffuse Hyperplastic Goiter
• Pathogenesis – TSH-mediated follicular cell stimulation • Compensatory mechanisms for iodine
Perchlorate Perchlorate deficiency (62 ug/L) (250 ug/L) – Increase efficiency of iodine trapping by follicular cells; increased NIS
– Preferential synthesis of T3 vs. T4 – TRH-TSH stimulation of follicular cell hypertrophy and hyperplasia with increased blood supply Grim, Tox. Pathol., 2009
Berlin 2017 Thomas Rosol 14 Diffuse Hyperplastic Goiter
• Functional significance; species differences – Lambs • Poor wool development • Dome-like skull • Delayed skeletal maturation • Signs of mental deficiency – Retardation of brain growth; decreased brain weight – Decreased arborization of dendritic tree of neurones; reduced thickness of molecular layer of cerebellum • Retrognathia (underdevelopment of the maxilla and/or maxilla)
Diffuse Hyperplastic Goiter
• Pet Birds – Intrathoracic location of the thyroid glands – Functional disturbances – Treatment • One drop of Lugol’s solution/ounce of drinking water per day – Prevention • One drop of Lugol’s solution/ounce of drinking water once per week (Lugol’s solution: 5 gm iodine/100 ml; 10 gm KI/100ml)
Berlin 2017 Thomas Rosol 15 Diffuse Hyperplastic Goiter
• Fish (captive) – Location of thyroids under operculum near gills – Change in diet provides inadequate iodine intake – Thyroid enlargement due to TSH-mediated follicular cell hypertrophy and hyperplasia
Colloid Goiter
• ‘Macofollicular’ goiter • Occurrence and etiology – Reduced severity of iodine deficiency: partial or complete correction
– Decreased demand for T4/T3 in young adults • Pathogenesis – Involutionary phase of hyperplastic goiter • Thyroid follicular response to decreased TSH • Decreased mobilization of colloid and secretion of thyroid hormones precedes reduction in synthesis of thyroglobulin (colloid)
Berlin 2017 Thomas Rosol 16 Exophthalmic Goiter
• Grave’s Disease with Hyperthyroidism – Humans, not animals – Different pathogenesis from feline hyperthyroidism
• Pathogenesis – LATS: Long acting thyroid stimulator • Autoantibody (7S IgG) produced by lymphoid tissue directed at TSH receptor of follicular cells
Iodide-Excess Goiter
• Horses, dogs, chicken, humans • Due to excess iodide intake • Pathogenesis
– Decreased secretion of T3 and T4 • Proteolysis of colloid diminished – Young animal • Iodine concentrated by placenta and mammary gland
Congenital Goiter Congenital Goiter Dyshormonogenesis Dyshormonogenesis • Species • Inherited; autosomal recessive – Sheep • Impaired thyroglobulin biosynthesis – Cattle – Defective processing of thyroglobulin mRNA – Goats – Sporadic in many species • Decreased T4 and T3 • Defect • Increased TSH – Impaired thyroglobulin synthesis • Increased iodide uptake by thyroid gland
Berlin 2017 Thomas Rosol 17 Goat: Congenital Goiter
Berlin 2017 Thomas Rosol 18 Nodular Goiter
• Adult to aged animals – Cats, horses, dogs, humans • Age-related, multifocal hyperplasia of follicular cells • Lesions – Macroscopic – Histologic • Separation of focal hyperplasia from adenoma of follicular cells
Thyroid Follicular Neoplasia Nodular Goiter Animals • Functional significance •Rats – Hyperplasia, adenoma, carcinoma (uncommon) – Euthyroid: Horses and dogs – More common in males •Mice – Hyperplasia, adenoma, carcinoma (uncommon) – Hyperthyroid: Humans and cats • Guinea pigs – adenoma and carcinoma •Cats – Multinodular goiter and adenomas • Dogs – Follicular carcinomas • Horses – Follicular adenomas
Berlin 2017 Thomas Rosol 19 Thyroid Follicular Neoplasia Humans • Thyroid cancer: Most common endocrine malignancy – Incidence has risen in past 4 decades – Uncommon deaths • Thyroid nodules are common – Palpable: 4-7% of adults – Ultrasound: up to 67%, usually women – Most are benign – 5-15% are malignant
Human Relevance Framework Thyroxine (T4) Rat Thyroid Follicular Tumors Serum Protein Binding • Fundamental differences in thyroid hormone Species TBG Postalbumin Albumin Prealbumin economy in rats Human ++ - ++ + – Rapid half-life of T4 Monkey ++ - ++ + – Lack of thyroid binding globulin Dog ++ - ++ - – High TSH concentrations (greater in males) Mouse - ++ ++ - – Sensitive to the tumorigenic effects of drugs that Rat - + ++ + decrease T or T Chicken - - ++ - 4 3 ______– Robust TSH response to decreased T4 or T3 TBG: Thyroxine (T4) Binding Globulin Prealbumin (Transthyretin, TTR)
Berlin 2017 Thomas Rosol 20 Rat Thyroid Gland
Human Relevancy Framework Nature’s Experiment Thyroid Hormone Economy Iodide Deficiency Goiter • Rats (esp. males) have increased incidence of • 200 million people proliferative lesions compared to humans likely due to increased TSH concentrations – Male rats have higher TSH compared to females • Severe hyperplasia – NOT preneoplastic • Rats have shorter half-life of T4 (12-24 h) vs. 5-9 days in humans – Due to less high affinity binding globulin, TBG, in rats • No increase in thyroid cancer • Rats require greater T4 (20 µg/kg) compared to humans (2.2 µg/kg) to substitute for the thyroid gland
Conundrum Thyroid Adenoma
• Why is TSH an indirect carcinogen in rats? – Gaps in knowledge – Genetics and epigenetics of thyroid follicular cells in rats FOLLICULAR PAPILLARY – Strain differences – Human relevance • TSH in humans – Only relevant in patients that develop thyroid cancer by some other mechanism
Berlin 2017 Thomas Rosol 21 Thyroid Adenoma: Horse
Follicular Adenoma: Rat
PAPILLARY ADENOMA
THYROID GLAND
Thyroid Carcinoma Dog • Mass in anterior cervical region • Local invasion • Metastases (≈ size of primary tumor) – Lung: early – Bone: Late (hypercalcemia) • Hyperthyroidism infrequent due to efficient enterohepatic metabolism and excretion
Berlin 2017 Thomas Rosol 22 Thyroid Carcinoma Dog: Breed Predisposition • Beagle (3.0*) *Odds Ratio • Siberian husky (2.5) • Golden retriever (2.2) • Shetland sheepdog (1.7) • Boxer (1.3) • Labrador retriever (1.2)
• No sex predisposition
Berlin 2017 Thomas Rosol 23 Follicular Adenocarcinoma Follicular/Compact Carcinoma
Compact Cellular ‘Solid’ Carcinoma Compact Cellular ‘Solid’ Carcinoma – TG IHC
Berlin 2017 Thomas Rosol 24 Capsular and Vascular Invasion Hemorrhage into Follicular Carcinoma
Undifferentiated Thyroid Carcinoma Anaplastic Carcinoma Anaplastic
• Small cell
• Giant cell
• Spindle cell
• Malignant mixed – Osteosarcoma – Chondrosarcoma
Anaplastic Carcinoma: Syncytial Cells Spindle Cell Carcinoma
Berlin 2017 Thomas Rosol 25 Spindle Cell Carcinoma: Thyroglobulin IHC Mixed Thyroid Carcinoma
Mixed Thyroid Carcinoma Malignant Ectopic Thyroid Tumors
Malignant Thyroid Tumors
• Papillary adenocarcinoma of thyroglossal duct remnants – Common in humans – Rare in dogs – Midline tumor – Low-grade malignancy
Berlin 2017 Thomas Rosol 26 PRIMARY THYROID NEOPLASMS BASE OF HEART (ANTERIOR MEDIASTINUM)
ORIGIN: ECTOPIC THYROID CELLS
Differential Diagnoses: 1) Malignant Lymphoma 2) Aortic Body Tumor
Berlin 2017 Thomas Rosol 27 Secondary (Metastatic) Thyroid Neoplasms Guinea Pig Thyroid Tumors
• Lymphoma • 4% of guinea pig cases at Northwest – Dogs Zoopath – Cattle • 2.5 to 6 yr. old • 50% malignant • Mammary carcinoma • Osseous metaplasia (osteoma) –Dog • Functional tumors – Associated with cardiomyopathy
Feline Hyperthyroidism Feline Hyperthyroidism
• Common in adult cats; dramatic increase since 1970’s • Possible cause (?) – Iodine in diet; Food dyes (iodine-containing); environmental goitrogens; environmental carcinogens (flame retardants) • Resembles Toxic Nodular Goiter in humans • Tissue can be transplanted to nude mice and will continue to secrete thyroid hormone – Autonomous
Thyroid Lesions in Hyperthyroidism: Cats Feline Hyperthyroidism • Clinical Signs • Multinodular (adenomatous) – Hyperactivity – Weight loss follicular hyperplasia – Increased apetite • Follicular adenoma – Bulky stools • Follicular adenocarcinoma – Thirst, polyuria – Hyperthermia (rare) – Tachycardia – Cardiomegaly
Berlin 2017 Thomas Rosol 28 Feline Hyperthyroidism Feline Hyperthyroidism: Abnormal Mineral Metabolism
• Lesions in • Hyperphosphatemia contralateral • Decreased serum ionized calcium thyroid gland • Increased serum PTH; PTG hyperplasia – Bilateral • Increased serum alkaline phosphatase – 70% of the – Bone type cases • Increased calcitriol • Decreased serum creatinine; increased GFR • Soft tissue mineralization
Berlin 2017 Thomas Rosol 29 Chief Cell Hypertrophy & Hyperplasia
Berlin 2017 Thomas Rosol 30 Thyroid C-cells
• Neuroectoderm • Migration from neural crest • Separate glands in fishes & birds (Ultimobranchial glands)
Berlin 2017 Thomas Rosol 31 Normal Ultimobranchial Body Calcitonin-Secreting Zebrafish C-Cells Submammalian Vertebrates Ultimobranchial Gland • Anatomically separate from thyroid gland
H = Heart; E = Esophagus zebrafish.org
Role of Calcitonin Stanniocalcin Fishes ‘Fish to Man and Back Again’
• Neurotransmitter • 1839: Hypocalcemic hormone discovered • Calcium regulation in fish • Role unclear – Corpuscles of Stannius (ventral to kidney) • Inhibits calcium transport by the gills • 1995: STC-1 discovered in mammals • Role during egg development (regulates phosphate, size, and • Potency in mammals reproduction) • Fish > Artiodactyl > Mammalian • STC-2 found in mammals • Stanniocalcin • Hypocalcemic factor from Corpuscles of • STC-2 found in fishes Stannius independent of calcitonin
Calcitonin Discovery
• Isolation of calcitonin in 1967 (Copp) – Collected 100 kg of ultimobranchial glands from 500,000 salmon in a fish packing plant in Vancouver, Canada – Biochemical purification – Amino acid sequence determined – Synthesized by Sandoz Pharmaceutical Co. (Basel) in the same year
Berlin 2017 Thomas Rosol 32 Calcitonin Content in Endocrine Glands Calcitonin Activity Gland (MRC units/mg) • Utimobranchial 4000-6000 • Salmon • Chicken • Thyroid 100-200 • Pig • Sheep • Human
Role of Calcitonin Pathophysiology of Calcitonin Mammals Mammals
• No clinical conditions associated with • No clinical conditions associated with calcitonin excess or deficiency calcitonin excess or deficiency • Prevents postprandial hypercalcemia and preserves the maternal skeleton •Biomarker: C-cell hyperplasia, tumors by inhibiting osteoclasts • Exogenous CT: hypocalcemia • Drug Tx: Hypercalcemia, osteoporosis
Calcitonin: Prevents excessive postprandial Calcitonin as a Rapid-Acting / bone resorption Fine Regulator Emergency Hormone Diet – Ca2+ Bone • Large stores of preformed in C-cells (Inhibits resorption) • CT receptors on osteoclasts and renal epithelium • Complete but transient inhibition of bone resorption Gastrin, Thyroid Calcitonin – Escape phenomenon Others C-cells release • Short plasma half-life (minutes) Ca2+ in diet
Berlin 2017 Thomas Rosol 33 Calcitonin Family of Peptides Calcitonin Family of Peptides Serum Calcium • Calcitonin – C-Cells (Prostate, CNS) • Calcitonin – Decrease serum calcium/Increase urine calcium – Hypocalcemia; Inhibits osteoclasts – Decrease osteoclastic bone resorption •CGRP • Calcitonin Gene-Related Peptide (CGRP) – Hypocalcemia (less potent than CT) – Neural tissues, C-cells • Amylin • Amylin – β cells of the pancreatic islets – Hypocalcemia (less potent than CT) – Co-secreted with insulin • Adrenomedullin • Adrenomedullin – many tissues – No effects on osteoclasts – Hypotensive effects
Calcitonin Family of Peptides Therapeutic Uses of Calcitonin Knockout Mice & Bone • Osteoporosis • Calcitonin/CGRP KO • Analgesia in vertebral fractures – Increased bone and trabeculae & resorption • Hypercalcemia - short lived effect • CGRP KO – Osteopenia; decreased bone formation • Amylin – Osteoporosis; decreased bone formation • Adrenomedullin KO: Lethal • CTR KO: Lethal • CTR +/-: Increased bone mass & formation Salmon calcitonin 100 times more potent than human calcitonin
Location of C-Cells in Thyroid C-Cell Complexes in Dogs
•Rat • Clusters in central gland and near the hilus – Central –C cells – Single cells to clusters; clusters increase with – Small undifferentiated cells age – Small, colloid-containing follicles •Dog – Cysts – Central, hilus (C-cell complexes) • Colloid containing; TG+ • Non-Human Primate • Do not accumulate iodide – Greater variability • Ultimobranchial remnants • Ungulates – Dispersed, single cells
Berlin 2017 Thomas Rosol 34 C-Cell Complexes in Dogs C-Cell Numbers
• Humans – < 1% of thyroid cells – May decrease with age •Rats – 5% of thyroid cells – Increase to 10% after 120 days – Individual cells (intrafollicular and parafollicular) – Interfollicular clusters • increase in number and size with age
C-Cell Distribution: Rat Thyroid Gland C-Cell Histomorphometry Cranial 1 2 • Immunostaining 2 3 • Tissue collection and embedding 3 • Sectioning consistency 4 • Landmarks 4 5 – Parathyroid glands
6 5 • 110,000 to 250,000 C-cells per rat – Wide variability per rat 7 – Consistent numbers in each gland Caudal 6
Martín-Lacave, Cell Tissue Res, 1992
Calcitonin Immunohistochemistry
• Human antiserum – Monkey, rat, mouse hamster, rabbit, guinea pigs • Porcine antiserum – Dogs, cats, cattle, pigs
Berlin 2017 Thomas Rosol 35 Calcitonin Secretogogues Thyroid C-cells: Pathological Conditions • Hyperplasia • Calcium (Ca2+), Mg2+, calcimemetics • Diffuse • GI Hormones • Focal • C-cell adenomas –Gastrin • Functional (secrete calcitonin) – Cholecystokinin • Non-functional –Secretin • C-cell carcinomas – Glucagon • Rare in domestic animals – Enteroglucagon (glicentin or oxyntomodulin) • Secrete calcitonin – GLP-1 (rodents) • Multiple endocrine neoplasia • Tumors of neuroendocrine origin • C-cell carcinoma + pheochromocytoma
Thyroid C-Cell Tumors Species Occurrence Factors Influencing
• Rat (F344, SD, WAG/Rij ) Development – Higher incidence in females (Wistar) • OVX decreases CT synthesis and secretion Thyroid C-Cell • Bull (ultimobranchial) Proliferative Lesions • Dog • Mouse • Irradiation •Horse • Ferret (with islet cell tumors) • Vitamin D • Mouflon (sheep) • Zebrafish (ultimobranchial) • High Dietary Calcium
Diffuse C-Cell Hyperplasia - Dog Diffuse C-Cell Hyperplasia
• Response to chronic stimulation – Hypercalcemia • Increase in number of follicles with C-cells – Intrafollicular and Parafollicular • Increase in number of C-cells per follicle • Increase in number of interfollicular C-cells
Berlin 2017 Thomas Rosol 36 Diffuse C-Cell Hyperplasia - Dog C-Cell Focal Hyperplasia
• Focal accumulation of C-cells
• Well delineated; Lack of compression
• Absence of a fibrous capsule
• Diameter < area of 5 average colloid-filled thyroid follicles (rats)
Focal C-Cell Hyperplasia - Rat Focal C-Cell Hyperplasia – Horse
C-Cell Adenoma
• Discrete, expansive nodule of C-cells • Well circumscribed, partially encapsulated • Variable compression (depending on size) of adjacent thyroid follicles • Neuroendocrine packeting – Abundant cytoplasmic area – Amphophilic cytoplasm • Wide size range (> 5 follicles to majority of the gland)
Berlin 2017 Thomas Rosol 37 Ultimobranchial Tumor: Zebrafish C-Cell Adenoma Horse
H = Heart; E = Esophagus zebrafish.org
C-Cell Adenoma Horse
Berlin 2017 Thomas Rosol 38 C-cell Adenoma Follicles - Horse C-cell Adenoma – Horse – CT IHC
Amyloid in C-Cell Tumors
• Produced by neoplastic cells • Usually confined to the tumor • Protein unrelated to immune amyloid • Similarity of amyloid and calcitonin – Shared amino acid sequences – Additional amino acid sequences of calcitonin gene product
C-Cell Carcinoma - Rat C-Cell Carcinoma - Rat
Berlin 2017 Thomas Rosol 39 C-Cell Carcinoma - Rat C-Cell Carcinoma - Rat
C-Cell Carcinoma - Dog C-Cell Carcinoma - Dog
Amyloid in C-Cell Carcinoma Rat C-Cell Immunohistochemistry
Calcitonin CGRP Chromogranin Somatostatin Normal +++ ++ ++ Rare Diffuse Rare, small +++ ++ ++ Hyperplasia clusters Focal ++ + + Few + cells Hyperplasia Adenoma ++ ++ + -/++ (Well Diff.) (homogeneous) (homogeneous) (homogeneous) (variable) Adenoma + + + -/++ (Pleiomorphic) (heterogeneous) (heterogeneous) (heterogeneous) (variable)
Carcinoma ++/+++ +/+++ +/+++ -/+++ (heterogeneous) (heterogeneous) (heterogeneous) (most +)
Berlin 2017 Thomas Rosol 40 C-Cell Histopathology: Mice
• Use immunohistochemistry – Normal C-cells – Diffuse hyperplasia – Early focal hyperplasia
• Can only see focal hyperplasia and tumors in routine histopathology
Mouse: Normal Diffuse Hyperplasia
Development of C-Cell Tumors C-Cell Carcinoma - Bull
• Irradiation
• High serum calcium – High dietary calcium (Bulls) – Chronic hypercalcemia – Excessive vitamin D • Conflicting data in rats
Berlin 2017 Thomas Rosol 41 C-Cell Carcinoma - Bull C-Cell Carcinoma - Bull
Development of C-Cell Tumors Tumorigenic Drugs in Rats
• Drugs and chemicals Drug Product Class – Direct or Indirect Exenatide GLP-1R agonist (F) Liraglutide GLP-1R agonist (M/F) – Mode of Action usually unknown Aledronate Bisphosphonate (M)
– Examples: Liraglutide, Exenatide, Arformoterol 2 receptor agonist (F) Aledronate, Arformoterol, Atenolol, Colesevelam, Naratriptan, Palonosetron Atenonol 2 receptor agonist (M) Colesevelam Bile acid sequestrant (F) – GLP-1 agonists (rats and mice only) Naratriptan 5-HT1D/1B receptor antagonist (M/F)
Palonosetron 5-HT3 receptor antagonist (F)
Glucose Homeostasis Fasting vs. Postprandial
• Fasting glucose level – Insulin – Glucagon • Postprandial glucose level – Incretin (GI) hormones • GLP-1 (glucagon-like peptide-1) • GIP (gastric inhibitory polypeptide; glucose-dependent insulinotropic polypeptide) • Only GLP-1 increases insulin in diabetics
Berlin 2017 Thomas Rosol 42 GLP-1 Exenatide (Byetta®) Very Short Half-Life in Blood
• Half-life: 1-5 minutes • First GLP-1 agonist (2005) • Synthetic form of exendin-4 • GLP-1 (7-36) amide and 7-37 forms – Isolated from Gila monster salivary glands – 50% homology to human GLP-1 • Degraded by plasma DPP-4 (dipeptidyl – Longer half-life in humans peptidase-4) • Adjunctive therapy for DM – DPP-4 inhibitors: Limited ability to increase • Twice daily injections GLP-1
Long-Acting GLP-1 Agonists C-cells and GLP-1 agonists Rats and Mice • Liraglutide (Victoza®) • C-cell hyperplasia – Modified rGLP-7-37 with palmitic acid moeity – Once daily injection – Diffuse • Bydureon® – Focal – Exenetide and microsphere formulation – Once weekly injection • Dulaglutide (once weekly) • C-cell adenomas – GLP (7-37) linked to Fc IgG fragment • Albiglutide (once weekly or biweekly) – GLP-1 dimer fused to albumin • C-cell carcinomas • Lixisenatide (once daily) • Rats are more sensitive than mice
GLP-1 Agonist-Induced C-cell Proliferation in Rodents
• Rodent-specific effect (?) Multiple • Receptor expression greatest in rodents • GLP-1R KO mice confirm role of receptor – Physiologic role in rodents Endocrine • No proliferation in dogs and NHP • No increase in calcitonin in dogs and NHP • Equivocal or no increase in calcitonin in humans Neoplasia • Long-term effect in humans need to be monitored
Berlin 2017 Thomas Rosol 43 Multiple Endocrine Neoplasia
MEN1 MEN2A MEN2B FMTC
Werner Syndrome Sipple Syndrome
Insulinoma, Pancreas gastrinoma, VIPoma Pituitary Adenoma
Parathyroid Hyperplasia Hyperplasia
C-Cell Yes 100% 100%
Pheo. Yes 50% RET MEN1 RET RET Genes NTRK1
Berlin 2017 Thomas Rosol 44