Hypothyroidism — guide.

What hypothyroidism is

Hypothyroidism is the condition in which the thyroid gland does not produce enough thyroid hormones, which slows down the metabolism of the entire body. Thyroid hormones regulate heart rate, body temperature, weight, bowel transit and cognitive function, so their deficiency affects almost all systems. The most common cause is Hashimoto autoimmune thyroiditis, in which the immune system gradually attacks the thyroid. The symptoms set in slowly and non-specifically, often being attributed to fatigue or age, which is why the disease is frequently underdiagnosed. The diagnosis is simple, through a blood test (TSH), and hormone replacement treatment restores metabolism to normal.

Causes

Hashimoto thyroiditis (the most common), post thyroid surgery, post radioactive iodine, medications (lithium, amiodarone), iodine deficiency and congenital forms.

Symptoms

Fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss, hoarse voice, depression, cognitive difficulties, bradycardia, eyelid edema and heavy menstrual periods. Severe hypothyroidism (myxedema) is a medical emergency.

Diagnosis

Elevated TSH + low FT4 = clinical hypothyroidism. Elevated TSH + normal FT4 = subclinical. Anti-TPO, anti-Tg antibodies for autoimmune thyroiditis. Thyroid ultrasound.

Treatment

Levothyroxine (L-T4) — Euthyrox, Letrox. Initial dose: 1.6 mcg/kg/day in adults. Adjustment based on TSH at 6-8 weeks. Take in the morning on an empty stomach, 30-60 min before breakfast.

TSH target: 0.5-2.5 mIU/l (individualized).

Important interactions

• Calcium, iron, magnesium — reduce L-T4 absorption (space them 4h apart).
• Coffee — space 30-60 min apart.
• Soy, fiber — similar effect.
• PPIs, antacids — reduce absorption.

OTC supplements

Strictly alongside L-T4:

• Selenium 100-200 mcg/day — reduces anti-TPO antibodies in Hashimoto.
• Vitamin D3 — frequent deficiency.
• Zinc.
• Iodine — ONLY in confirmed deficiency (excess can worsen it!).

DO NOT use animal thyroid extracts or high-dose iodine without medical supervision.

Medical disclaimer: the information in this guide is for informational purposes only and does not replace the advice of a doctor or pharmacist. For diagnosis and treatment, consult a healthcare professional.