Thyroid problems – under-active and over-active
Tiredness, weight change, feeling cold or wired — thyroid symptoms are vague enough to be missed for years, and the test is straightforward.
One gland, two opposite problems
The thyroid sets the pace of the body's metabolism. Producing too little slows everything down; producing too much speeds everything up. Both are common, both are treatable, and both are frequently attributed to stress or age for years first.
- Under-active: tiredness, weight gain, feeling cold, dry skin, hair thinning, constipation, low mood, heavy periods, slowed thinking.
- Over-active: weight loss despite eating well, feeling hot, sweating, palpitations, tremor, anxiety and irritability, loose stools, disturbed sleep, eye changes.
- Either can cause a swelling at the front of the neck — a goitre.
Treatment for an under-active thyroid
Replacing the missing hormone is straightforward, effective and inexpensive, and is usually lifelong.
The standard replacement:
Levothyroxine (T4) — Euthyrox, Eltroxin, Synthroid, Thyrax
Hypothyroidism; thyroid hormone replacement; TSH suppression post-thyroid cancer
- Take it on an empty stomach, usually first thing, with water.
- Wait before eating, and separate it by several hours from iron, calcium, antacids and some other medicines, which block its absorption.
- Take it every day at the same time — this is one where consistency genuinely changes the blood level.
- Expect blood tests every few weeks while the dose is adjusted, then periodically once stable.
- Improvement takes weeks rather than days.
Treatment for an over-active thyroid
Options are medicines that reduce hormone production, radioactive iodine, or surgery. The choice depends on the cause, on age and on whether pregnancy is a consideration, and it is a specialist decision.
Used to control an over-active thyroid:
Carbimazole — Neo-Mercazole
Hyperthyroidism (Graves' disease; toxic goitre)
Propylthiouracil (PTU) — Propylthiouracil
Hyperthyroidism; thyroid storm; first trimester of pregnancy (preferred over carbimazole)
Propranolol — Inderal, Adco-Propranolol
Hypertension; angina; essential tremor; anxiety (performance); migraine prophylaxis; thyrotoxicosis symptoms
Thyroid and pregnancy
Thyroid problems in pregnancy affect the baby's development, and requirements change as pregnancy progresses. Anyone on thyroid treatment who becomes pregnant or is planning to should tell their clinic early — the dose usually needs adjusting and monitoring becomes more frequent. This is not a reason to stop treatment; untreated is considerably more dangerous.
Common questions
- Can diet or iodine fix a thyroid problem?
- Iodine deficiency is not a common cause in South Africa, where table salt is iodised. Taking iodine or kelp supplements can actually worsen thyroid disease. Diet does not replace treatment.
- Will I be on treatment forever?
- For an under-active thyroid, usually yes, and it is a simple daily tablet. For an over-active thyroid, some people remit after a course of medicine, while others need definitive treatment.
- Is a lump in my neck a thyroid problem?
- It may be a thyroid nodule, which are common and usually benign — but any new neck lump should be examined, and one that is growing, hard, or comes with a hoarse voice or difficulty swallowing needs prompt assessment.
Sources
- Primary Healthcare Standard Treatment Guidelines and Essential Medicines ListNational Department of Health, South Africa
- Adult Primary Care guideNational Department of Health, South Africa
Last reviewed 4 August 2026.