Thyroid and Parathyroid Disorders Overview

Thyroid and Parathyroid Disorders

• Endocrine glands release chemical messengers (hormones) into the bloodstream
• The hypothalamus sends signals to the pituitary gland
• The anterior pituitary receives hormonal signals from the hypothalamus and sends out further signals
• The posterior pituitary releases hormones synthesized by the hypothalamus
• End organs are targets for pituitary hormones and may secrete additional hormones

Endocrine Disorders: Assessment and Diagnosis

• Assess current and past medical history
• Some disorders have wide-ranging multi-system signs that may affect mood and behavior
• Analyze immunoassays or blood levels of hormones
• Urinary hormone levels are sometimes analyzed
• Urine collection over 24 hours may be necessary
• Suppression/stimulation tests may be used
• CT, MRI, or ultrasound scans may be utilized

Hormone Replacement Therapy

• Dosage schedules attempt to mimic physiological effects
• Common replacements include glucocorticoids, thyroid hormones, sex steroids, and ADH

Suppression of Hormone Overproduction

• Medications, surgery, or radiation can be used to suppress hormone overproduction

Thyroid

• Triiodothyronine (T3) and thyroxine (T4) are produced

• Iodine is required for T3 & T4 synthesis

• T4 regulates body metabolism

• Thyroid disorders are more common in women

• Primary thyroid disorders are common

• Enlarged thyroid can indicate hypo- or hyperfunction

Goiter

• Goiter is an enlargement of the thyroid gland
• Causes could include excess TSH, low iodine levels, or goitrogens (foods that promote gland enlargement)
• May or may not cause thyroid dysfunction symptoms

Hypothyroidism

• Hashimoto's thyroiditis is an autoimmune disorder with anti-thyroglobulin and anti-thyroperoxidase antibodies as primary indicators.
• Other causes include drugs and genetics (especially postpartum thyroiditis/ high incidence or congenital hypothyroidism)
• Common symptoms of hypothyroidism include cold intolerance, weight gain, lethargy, fatigue, memory deficits, poor attention span, and brittle nails.
• Muscle cramps, constipation, decreased fertility, a puffy face, and hair loss can also occur.

Hypothyroidism: Systemic Effects

• Reduced LDL receptors cause hyperlipidemia
• Elevated carotene causes yellow-orange skin
• Decreased hematopoiesis leads to anemia
• Decreased renal function increases susceptibility to drug toxicity
• Myxedema is severe hypothyroidism

Thyroid Disorders: Screening

• The American Thyroid Association recommends screening women at age 35, and every 5 years thereafter.
• The American College of Physicians recommends screening women aged 50 or older with clinical features of thyroid disorder.
• Neonatal screening tests assess for elevated TSH levels. It identifies 90% of congenital hypothyroidism cases.

Hypothyroidism: Diagnosis and Treatment

• Primary hypothyroidism is diagnosed with high TSH and low free T3 & T4
• Secondary hypothyroidism is diagnosed with low TSH, low free T3, and low free T4.
• Hashimoto's thyroiditis is diagnosed with anti-thyroglobulin antibodies and anti-thyroperoxidase antibodies.
• Ultrasound, blood tests, and screenings are other diagnostic tools.
• Treatment is mainly hormone replacement therapy (e.g., levothyroxine).
• Myxedema coma is severe hypothyroidism which progresses to confusion and coma if untreated.

Hyperthyroidism

• Elevated free T3 and free T4 levels indicate hyperthyroidism, commonly due to Graves' disease.
• Autoimmune stimulation of the thyroid gland is a common cause
• Specific HLA and tissue types are also involved.
• Thyroid-stimulating immunoglobulins (TSI) and TSH receptor antibodies (TRAb) are indicators
• Other causes include subacute thyroiditis, postpartum period thyroiditis, thyroid adenoma, excessive TSH, toxic multinodular goiter, excess iodine ingestion, and Jod-Basedow syndrome.

Hyperthyroidism: Signs and Symptoms

• Symptoms include nervousness, insomnia, sensitivity to heat, weight loss, enlarged thyroid gland, atrial fibrillation, increased heart rate, and increased sympathetic nervous system sensitivity.
• Exophthalmos (bulging eyes), wide-eyed stare, extraocular area filled with mucopolysaccharides, Grave's ophthalmopathy, and periorbital edema are additional symptoms.

Hyperthyroidism: Diagnosis and Treatment

• Diagnosis includes Graves' disease (serum thyrotropin receptor antibodies), radioactive iodine uptake (RAIU) tests, ultrasound with color Doppler evaluations, and blood tests (TRH, TSH, T3, and T4 Levels).
• Note: Biotin supplements may interfere with thyroid test accuracy
• Treatment options include antithyroid hormone medications (e.g., propylthiouracil (PTU), carbimazole), radioactive iodine-131 ablation, and/or surgical intervention.

Hypothyroidism vs. Hyperthyroidism

• Hypothyroidism symptoms include hypercholesterolemia, weight gain, decreased fertility, sluggishness, cold sensations, constipation, lethargy, and fatigue
• Hyperthyroidism symptoms include anxiety, tremors, tachycardia, feeling warm, weight loss, exophthalmos (bulging eyes), atrial fibrillation, and decreased fertility

Thyrotoxic Crisis (Thyroid Storm)

• Severe condition of high thyroid hormone levels
• Overwhelming release of thyroid hormones, with serum-free T4 total T3 levels being elevated and TSH levels usually undetectable.
• Causes include surgery or trauma
• High fever, tachycardia, agitation, and psychosis are common indicators of this medical emergency.

Thyrotoxic Crisis (Thyroid Storm): Management

• Methods to lessen thyroid hormone synthesis include methimazole or PTU
• Inhibiting thyroid hormone secretion with potassium iodide (oral or intravenous) may help
• Reducing heart rate with beta blockers and/or calcium channel blockers is beneficial
• Circulatory support, like stress doses of intravenous glucocorticoids, is crucial.

Thyroid Nodules

• Nodules are usually asymptomatic
• Hypothyroidism or hyperthyroidism can sometimes be present.
• Single nodules or multiple nodules may be present and associated with an increased risk of malignancy.
• Ultrasounds and needle biopsies are critical for diagnosis
• Radioactive isotopes like Tc-scan can assist in nodule diagnosis (hot, warm, cold).

Malignant Thyroid Nodule

• Factors associated with malignant thyroid nodules include age (under 20 or over 70), male sex, history of neck irradiation, a firm, hard, or immobile nodule, and/or presence of cervical lymphadenopathy.

Parathyroid Gland

• Four pea-sized glands situated on the posterior thyroid secrete parathyroid hormone (PTH)
• PTH is released when blood calcium levels are low
• PTH regulates bone resorption, intestinal calcium absorption, and kidney processes.

Hypoparathyroidism and Hyperparathyroidism

• Hypoparathyroidism is rare, often caused by thyroid surgery, and leads to hypocalcemia symptoms
• Hyperparathyroidism (parathyroid adenoma) manifests with high PTH and calcium levels. This can be primary (benign tumor) or secondary (response to low calcium).
• Diagnosis involves blood tests for PTH and calcium levels.
• Treatment involves parathyroidectomy for primary cases while secondary cases focus on lowering elevated calcium levels

Alert!

• Myxedema coma is a severe hypothyroidism complication
• Thyrotoxic crisis (thyroid storm) is a life-threatening condition due to high thyroid hormone levels. Early intervention is crucial.

Explore the key concepts surrounding thyroid and parathyroid disorders, including hormone release from endocrine glands, the role of the hypothalamus and pituitary gland, and methods for assessing and diagnosing endocrine disorders. This quiz also covers hormone replacement therapies and their physiological implications.