07/25/2025
The thyroid gland, a butterfly-shaped organ in the neck, produces thyroid hormones (triiodothyronine, T3; thyroxine, T4) that regulate metabolism, energy levels, body temperature, and growth. Disorders of the thyroid arise from abnormal hormone production (too much or too little) or structural issues, with wide-ranging effects on bodily functions. Below is a detailed breakdown of common thyroid gland disorders:
Hyperthyroidism
A condition where the thyroid gland produces excess T3 and T4, accelerating the bodyโs metabolic rate.
Causes
Gravesโ disease (most common, ~70% of cases): An autoimmune disorder where antibodies (TSH receptor antibodies) stimulate the thyroid to overproduce hormones.
Toxic multinodular goiter**: Enlarged thyroid with multiple nodules that independently secrete excess hormones.
Toxic adenoma: A single benign thyroid nodule that overproduces hormones.
Thyroiditis (inflammation): Temporary hyperthyroidism occurs when inflamed thyroid cells release stored hormones (e.g., subacute thyroiditis).
Key Symptoms
Increased metabolic rate: Weight loss (despite increased appetite), rapid heartbeat (tachycardia), palpitations.
Nervous system: Anxiety, irritability, tremors, insomnia.
Sensory/physical: Heat intolerance, excessive sweating, thinning skin, brittle hair.
Musculoskeletal: Muscle weakness, fatigue (paradoxically, due to increased energy expenditure).
Diagnosis
Blood tests: Low thyroid-stimulating hormone (TSH, since excess T3/T4 suppresses pituitary TSH release) + high free T3/T4.
For Gravesโ disease: Presence of TSH receptor antibodies.
Imaging: Thyroid ultrasound (to detect nodules) or radioactive iodine uptake (RAIU) test (Gravesโ disease shows *increased* uptake; thyroiditis shows *decreased* uptake).
Treatment
Antithyroid drugs: Methimazole or propylthiouracil (PTU) block hormone synthesis. Used for mild cases or before other treatments.
Radioactive iodine (RAI) therapy: Oral radioactive iodine is absorbed by thyroid cells, destroying overactive tissue. Often leads to hypothyroidism (requiring lifelong hormone replacement).
Thyroidectomy: Surgical removal of part or all of the thyroid (reserved for large goiters, pregnancy, or RAI contraindications). Also may cause hypothyroidism.
Hypothyroidism
Definition: The thyroid produces insufficient T3 and T4, slowing metabolism.
Causes
Hashimotoโs thyroiditis (most common, ~90% of cases): Autoimmune destruction of thyroid cells, leading to gradual hormone decline.
Iatrogenic: Post-thyroidectomy, radioactive iodine therapy, or radiation to the neck.
Congenital: Rare genetic defects causing underdeveloped thyroid (congenital hypothyroidism).
Iodine deficiency: Rare in iodine-replete regions but still a global cause (iodine is essential for thyroid hormone production).
Key Symptoms
Decreased metabolic rate: Weight gain (despite reduced appetite), bradycardia (slow heartbeat), cold intolerance.
Nervous system: Fatigue, brain fog, depression, memory problems.
Skin/hair: Dry skin, brittle nails, hair loss (including eyebrows).
Digestive: Constipation.
Reproductive: Menstrual irregularities (heavy/painful periods), infertility.
Diagnosis
Blood tests: High TSH (pituitary compensates for low T3/T4) + low free T3/T4.
For Hashimotoโs: Presence of thyroid peroxidase antibodies (TPOAb) or thyroglobulin antibodies (TgAb).
Treatment
Hormone replacement: Lifelong oral levothyroxine (synthetic T4), which the body converts to T3. Dosage is adjusted based on TSH levels.
Monitoring: Regular blood tests (every 6โ12 months once stable) to ensure optimal hormone levels.