Coagulation and Hormone Assays

Vocabulary flashcards covering coagulation pathways, platelet disorders, factor deficiencies, clinical signs, secondary hemostatic testing, and endocrine hormone assays.

Coagulation

The formation of a blood clot that slows or stops bleeding when blood vessels are cut or damaged; also termed hemostasis or clotting.

Coagulopathy

Any disorder or abnormality of blood coagulation.

Primary Hemostasis

The initial stage of blood clotting involving the activation and aggregation of platelets to form a platelet thrombus (plug).

Secondary Hemostasis

The stage of blood clotting involving the activation of coagulation factors to form fibrin strands, which stabilize the primary platelet thrombus.

Thrombocyte

A clotting cell (platelet) produced in the bone marrow by megakaryocytes that forms the primary matrix for a blood clot.

Megakaryocyte

The large bone marrow cell responsible for producing thrombocytes (platelets).

Thrombocytopenia

An abnormally low platelet count in the blood, representing the most common platelet disorder in animals.

von Willebrand Factor

A factor that acts alongside thrombin on platelets to make them sticky so they adhere to exposed collagen fibrils at sites of vessel injury.

Coagulation Cascade

A multi-step biochemical process involving 12 plasma factors (labeled with Roman numerals I–XIII, omitting VI) and calcium ions ($\text{Ca}^{2+}$) that results in fibrin formation.

Fibrin

An insoluble protein derived from fibrinogen through the action of thrombin that forms a thread-like meshwork to embed platelets and stabilize a clot.

Thrombin

An enzyme formed from prothrombin (Factor II) via prothrombinase that enables platelet aggregation and cleaves fibrinogen into fibrin.

Extrinsic Pathway

A coagulation pathway initiated at the site of tissue injury when injured tissues release Tissue Factor (Factor III).

Intrinsic Pathway

A coagulation pathway initiated when blood cells come into contact with exposed endothelial surfaces.

Common Pathway

The pathway where the intrinsic and extrinsic coagulation pathways converge at Factor X to proceed to fibrin formation.

Factor XII (Hageman Factor)

A coagulation factor whose deficiency causes an asymptomatic clotting defect commonly observed in dogs and cats.

Factor IX (Christmas Factor)

A coagulation factor whose deficiency causes Hemophilia B (Christmas Disease), notably reported in Cairn Terriers.

Factor VIII

A coagulation factor whose deficiency causes Hemophilia A in many species.

Disseminated Intravascular Coagulation (DIC)

A secondary disorder characterized by excessive clotting factor/platelet consumption and increased fibrinolysis, leading to elevated fibrin degradation products (FDPs) and severe hemorrhage.

Fibrinolysis

The natural enzymatic process of blood clot dissolution.

Petechia

Pinpoint, non-raised, round purplish-red spots on skin or mucous membranes caused by minor capillary bleeding.

Ecchymosis

A non-elevated, round or irregular blue/purplish patch of hemorrhage larger than a petechia.

Hemarthrosis

Bleeding into a joint cavity, serving as a clinical sign of severe coagulopathy.

Prothrombin Time (PT)

A secondary hemostatic test that evaluates the extrinsic and common pathways; highly sensitive for early Vitamin K deficiency (rodenticide toxicity).

Activated Partial Thromboplastin Time (aPTT)

A secondary hemostatic test that evaluates the intrinsic and common pathways; prolonged in factor deficiencies and DIC.

Buccal Mucosal Bleeding Time (BMBT)

A primary hemostatic screening test performed by making an incision on the gingival surface and recording the time required for bleeding to stop.

Thyroxine (T4)

An iodine-containing hormone formed from thyroglobulin in the thyroid gland; measured as Total T4 or Free T4 (unbound) to evaluate thyroid status.

Triiodothyronine (T3)

The active form of thyroid hormone, affected by non-thyroidal systemic illness.

Hyperthyroidism

The most common endocrine disorder in elderly cats ($> 10\,\text{years}$ of age), characterized by polyphagia, weight loss, and behavior changes.

Hypothyroidism

An endocrine disorder most commonly seen in dogs, caused by lymphocytic thyroiditis or idiopathic thyroid atrophy, leading to lethargy, obesity, and symmetric alopecia.

T3 Suppression Test

A diagnostic test for feline occult hyperthyroidism where T3 is administered ($25\,\mu\text{g}$ TID for $2.5\,\text{days}$) to evaluate if T4 blood levels suppress normally.

Thyroid Stimulating Hormone (TSH)

A hormone produced by the pituitary gland that stimulates the release of T4 from the thyroid gland.

Parathyroid Hormone (PTH)

A hormone secreted by the parathyroid gland that functions alongside calcitonin to regulate blood calcium levels.

Cortisol

A glucocorticoid hormone produced by the adrenal cortex in response to ACTH stimulation from the pituitary gland.

Cushing's Disease

Hyperadrenocorticism; a state of excessive cortisol secretion caused by adrenal gland dysfunction or an ACTH-secreting pituitary tumor.

Addison's Disease

Hypoadrenocorticism; a condition defined by deficient adrenocortical hormone production.

ACTH Stimulation Test

A diagnostic test where baseline cortisol is measured, synthetic ACTH (Cortrosyn) or ACTH gel is administered, and post-injection cortisol is measured $1\,\text{hour}$ later.

Low Dose Dexamethasone Suppression Test (LDDST)

A screening test for Cushing's disease involving blood collection before and at $4\,\text{hours}$ and $8\,\text{hours}$ after IV administration of $0.01\,\text{mg/kg}$ dexamethasone sodium phosphate.

Insulin

A hormone produced by the islet cells of the pancreas that allows blood glucose to enter body cells for nourishment.

Insulinoma

A tumor of the pancreatic islet cells that secretes excessive insulin, leading to persistent hypoglycemia; commonly encountered in ferrets.

Diabetes Mellitus

A disease marked by insufficient insulin production, persistent hyperglycemia, glucosuria, and potential ketonuria.

Fructosamine

A stable compound created when glucose binds to serum proteins (primarily albumin), reflecting average blood glucose levels over the preceding $1\text{--}2\,\text{weeks}$.

Glycated Hemoglobin (A1C)

A compound formed in erythrocytes when glucose binds with hemoglobin, reflecting blood glucose control over the preceding $60\text{--}90\,\text{days}$.

Progesterone Assay

A hormone test used during estrus in the bitch to detect the initial progesterone rise (coinciding with the LH peak) and predict ovulation timing.