Hypothyroidism
Also known as Underactive thyroid
This article is general health information for the selected condition. It is not a diagnosis and does not replace clinical judgement. If you have questions or need treatment advice, please consult a qualified healthcare professional.
What is hypothyroidism?
Hypothyroidism occurs when the thyroid gland produces too little thyroid hormone, slowing metabolism. Symptoms are common and non specific, which is why it is diagnosed by blood test rather than by symptoms alone. Replacement with levothyroxine is straightforward and effective when dosing and absorption are handled correctly.
Causes
- Autoimmune thyroiditis, known as Hashimoto disease
- Thyroid surgery or radioiodine treatment
- Certain medicines including amiodarone and lithium
- Iodine deficiency in some regions
- Congenital thyroid problems
- Pituitary disease in rare central cases
Symptoms
- Fatigue and sluggishness
- Weight gain despite unchanged diet
- Feeling cold when others do not
- Dry skin and hair thinning
- Constipation
- Low mood and poor concentration
- Heavy or irregular periods
- Muscle aches and slowed reflexes
Risk factors
- Female sex
- Age over 60
- Family history of thyroid or autoimmune disease
- Other autoimmune conditions such as type 1 diabetes or celiac disease
- Previous neck radiation
- Postpartum period
Diagnosis
- Raised TSH with low free T4 in overt disease
- Raised TSH with normal free T4 in subclinical disease
- Thyroid peroxidase antibodies to confirm autoimmune cause
- Repeat testing before starting lifelong treatment
- Full blood count and coeliac screening where relevant
Treatment
- Levothyroxine taken on an empty stomach
- Separating the dose from calcium, iron and antacids by four hours
- Retesting TSH six to eight weeks after any dose change
- Dose increase in pregnancy, usually early and substantial
- Annual monitoring once stable
Self care
- Take levothyroxine on an empty stomach, 30 to 60 minutes before food
- Separate it from calcium, iron and antacids by at least four hours
- Take it at the same time every day
- Do not switch brands without telling your doctor
- Attend blood tests six to eight weeks after any dose change
- Report pregnancy immediately, since the dose usually needs increasing
When to see a doctor
Book an appointment if:
- Persistent fatigue, weight gain or cold intolerance
- Symptoms continuing despite normal blood results
- Palpitations, tremor or anxiety suggesting the dose is too high
- Planning pregnancy or newly pregnant
- New neck swelling or difficulty swallowing
- Before starting medicines that affect absorption
Some symptoms need emergency care rather than an appointment. See the warning signs listed above.
Prevention
- Hypothyroidism generally cannot be prevented
- Adequate dietary iodine prevents deficiency related cases
- Monitor thyroid function after thyroid surgery or radioiodine
- Check thyroid function on amiodarone or lithium
- Screen if you have another autoimmune condition
Outlook
Hypothyroidism is straightforward to treat and levothyroxine restores normal thyroid levels in almost everyone. Treatment is usually lifelong, and most people feel completely well once the dose is right. Some report residual symptoms despite normal blood results, which warrants review of dose timing, absorption and other contributing conditions.
Common questions
Why must levothyroxine be taken on an empty stomach?
Food, coffee, calcium and iron significantly reduce absorption. Taking it 30 to 60 minutes before breakfast, or at bedtime well after eating, keeps levels consistent.
Does hypothyroidism explain weight gain?
It can cause modest weight gain, often a few kilograms, largely from fluid retention. Correcting the hormone level rarely produces large weight loss on its own.
Why is thyroid function checked in pregnancy?
Thyroid hormone is essential for fetal brain development and requirements rise early in pregnancy. Women on levothyroxine usually need a dose increase as soon as pregnancy is confirmed.
References
Important: Dard AI is not a medical device and does not diagnose, treat, or replace clinician judgement. This article is general information only. Always consult a qualified healthcare professional about diagnosis and treatment, and seek emergency care for severe or rapidly worsening symptoms.