18. Endocrine Disease Flashcards
T4 assay
T4 assay (thyroxine test) is elevated in 90% of patients with hyperthyroidism and depressed in 85% of patients with hypothyroidism
T3 test
Checks for levels of triiodothyronine and abnormally high level usually indicates Graves’ disease.
T3 is used to detect hyperthyroidism if T4 is measured to be normal, as T3 may be the only hormone in excess.
T3 can be low due to various factors that impair conversion of T4 to T3 (euthyroid sick syndrome)
Gold standard for diagnosis and treatment of thyroid dysfunction and useful in detecting hypothyroidism
TSH test
Normal TSH level
0.4 to 4.0 mIU/L
In primary hypothyroidism, levels are greater than 20 mIU/L.
During treatment of hypothyroidism, goal of thyroid replacement therapy is to normalize TSH levels.
What is hyperthyroidism
Hyperthyroidism is a condition in which the thyroid gland is overactive and exposes the body tissues to excessive amounts of thyroid hormone.
Etiology: multinodular diffuse goiter and Graves’ disease
Manifestations: warm skin, sweating, increased ventricular contractility, tachycardia, elevated systolic BP, weight loss, diarrhea, palpitations, emotional lability, skeletal muscle weakness, restlessness, heat intolerance.
Graves’ disease patients might exhibit exophthalmos from increased volume of retro-orbital fat
What is Graves’ disease?
Autoimmune condition which results in hyperstimulation of TSH receptors from autoantibodies produced by the immune system. Most common cause of hyperthyroidism.
Goiters, exophthalmos, and pretipial myxedema.
How is Graves’ disease treated?
Antithyroid drugs (reduce production of thyroid hormone)
Other modalities include radioiodine therapy and thyroidectomy.
What is Plummer’s disease?
Toxic multinodular goiter
Thyroid contains autonomously functioning thyroid nodules with resulting hyperthyroidism.
Does NOT cause exophthalmos and pretibial myxedema seen in Graves’
Propranolol, radioiodine therapy, thyroidectomy.
What is Thyroid Storm?
Acute exacerbation of hyperthyroidism that is life threatening, and occurs most commonly in undiagnosed or undertreated hyperthyroid patient.
- Triggers = stress of surgery, non-thyroid illness
- Hypermetabolic state caused by excessive release of thyroid hormones
- Dysrhythmias, myocardial ischemia, congestive heart failure, hyperthermia, shaking, change in consciousness, nausea, vomiting, diarrhea, and tachycardia. Heart failure and pulmonary edema can rapidly occur and cause death.
- Early sign = very elevated systolic pressure and low diastolic pressure.
Antithyroid drugs
Propylthiouracil
Methimazole
Prevent production of T4 and conversion of T3 from T4
Propranolol can also be used to control symptoms of sympathetic activation (palpitations, trembling, anxiety).
How is thyroid storm treated?
Less severe: supportive measures such as cooling blankets, IV fluids, electrolyte correction, EKG monitoring, oxygen supplementation, and medicine to manage agitation.
Severe: further medication with sodium iodide (blocks release of stored thyroid hormone), propylthiouracil, hydrocortisone (prevents conversion of T4 to T3) and propranolol.
Patient management with hyperthyroidism
Have patient reach euthyroid state and resting HR <85bpm prior to surgery with normal thyroid function tests.
- Emergency surgeries - beta blocker (propranolol), glucocorticoids (decrease hormone release and reduce peripheral conversion of T4 to T3
- Avoid sympathomimetic agents such as ketamine, epinephrine, atropine, ephedrine
- Monitor EKG
What is hypothyroidism?
Hypothyroidism (also known as myxedema) is a common condition where the thyroid gland has decreased production of thyroid hormone resulting in inadequate circulating levels of T4 or T3 or both. Disease development can be insidious and patients often have no or only mild symptoms, making diagnosis difficult.
Signs and symptoms of hypothyroidism
Generalized reduction in metabolic activity, cardiac and respiratory depression, fatigue, slow mental functioning, hyponatremia, constipation, cold intolerance, slow movement, depression, constipation, thinning of the hair, hair loss, weight gain, thickened tongue, thyroid nodule, periorbital edema, bradycardia.
Primary vs. secondary hypothyroidism
Primary: thyroiditis (Hashimoto’s disease), medications (iodine, propylthiouracil, methimazole), iodine deficiency, irradiation to neck, hereditary defects in biosynthesis, previous treatment with radioactive iodine, previous thyroidectomy).
Secondary: hypothalamic or pituitary disease
Lab values in Hashimoto’s thyroiditis (T3, T4, TSH)
Low T4 and T3
High TSH
Presence of antibodies against thyroid peroxidase (TPO)
Normal level of TSH reliably excludes hypothyroidism
What is myxedema?
A state of decompensated hypothyroidism characterized by hypoglycemia, hypercapnia, hypoventilation, hypotension, susceptibility to cardiac dysrhythmias, hypothermia, stupor or coma, delirium, hyponatremia.
Treated with IV T4 or T3, glucocorticoid therapy, airway management, supportive measures.
What is Diabetes Mellitus?
DM is a metabolic disorder which results in a defect in insulin secretion, action, or both, resulting in hyperglycemia.
What is Type I diabetes?
Type I diabetes mellitus (insulin-dependent diabetes mellitus) is due to impaired production of insulin and occurs early in life.
- Loss of insulin-producing beta cells of the islet of Langerhans in the pancreas due to an autoimmune process and results in low level of circulating insulin.
What is type 2 diabetes mellitus
Occurs due to an altered number and affinity of peripheral insulin receptors and generally occurs later in life. May also have features of reduced insulin secretion.
- Etiology primarily lifestyle factors and genetics.
Function of insulin
Increase glycogen synthesis, decrease gluconeogenesis, increase potassium uptake, and increase lipid synthesis.
- Elicits a drastic increase in uptake of glucose by cells, especially in skeletal muscle cells.
Diagnostic criteria for DM
Fasting glucose >126 mg/dL on 2 or more occasions
Glucose tolerance test (ratings greater than 200mg/dL 2 hours after 75gram glucose load)
HgB A1C of 6.5 or greater
Non-fasting plasma glucose >200mg/dL and symptoms of DM
DM sequelae
Peripheral neuropathy
Coronary disease at young age
Silent ischemic episodes due to myocardial neuropathy
Diabetic nephropathy
Diabetic retinopathy
Ischemic heart disease due to glycosylation of LDLs
Diabetic cheiroarthropathy (limited joint mobility of hands).
What is insulin?
Types
Insulin promotes the uptake of glucose into muscle, adipose, and liver tissue.
- Fast acting (lispro, aspart)
- Short acting (regular)
- Intermediate acting (NPH, lente)
- Prolonged acting (Glargine, levemir)
- Combined insulin treatment = Novolog (70% aspart protamine and 30% aspart) and Humolog (75% lispro protamine and 25% lispro)
List some oral hypoglycemics
- Biguanides (Metformin)
- Sulfonylureas (Glipizide, Glyburide)
- Thiazolidinediones (Rosiglitazone, Pioglitazone)
- Meglitinides (Repaglinide)
- GLP1 agonist (Exantide/Byetta)
- DPP4 inhibitor (Sitagliptin/Januvia)
How do biguanides (Metformin) work?
Biguanides (Metformin): decrease hepatic gluconeogenesis and decrease intestinal glucose absorption. Risk of lactic acidosis in setting of renal insufficiency with usage.
How do sulfonylureas (Glipizide, Glyburide) work?
Stimulate beta cells to produce insulin (risk of hypoglycemia with usage)
How do thiazolidinediones work? (Rosiglitazone, Pioglitazone)
Work intracellularly to promote insulin sensitivity in adipose, hepatic, and muscle tissue. Also decrease triglycerides and increase HDL. Weight gain is a side effect.
What is diabetic ketoacidosis?
DKA is a metabolic condition that occurs secondary to an insulin shortage that results in hyperglycemia, ketonemia, and an anion gap metabolic acidosis.
Signs/symptoms of DKA
Vomiting, confusion, polydipsia, polyuria, dehydration, abdominal pain, Kussmaul breathing, hyperglycemia, hyperkalemia, ketotic “fruity” breath, dry mucous membranes, and hypotension
