Condition

Hypothyroidism: Underactive Thyroid — Symptoms & Treatment

Hypothyroidism is one of the most common endocrine disorders, affecting mainly women. It's easily diagnosed with a blood test and highly treatable with daily levothyroxine.

Prevalence
~5% women; ~1% men
Most common cause
Hashimoto's thyroiditis
Diagnosis
TSH + Free T4 blood test
Treatment
Daily levothyroxine (T4)

Common Symptoms

SystemSymptoms
MetabolismWeight gain, cold intolerance, low body temperature, slow heart rate
EnergyFatigue, lethargy, poor concentration ('brain fog'), depression
Skin/Hair/NailsDry skin, hair loss, brittle nails, non-pitting oedema (myxoedema)
GutConstipation, reduced appetite
ReproductiveHeavy periods, reduced fertility, elevated prolactin
CardiovascularRaised cholesterol, raised diastolic BP, pericardial effusion (severe)
NeuromuscularMuscle cramps, carpal tunnel syndrome, peripheral neuropathy
Check TSH FirstA normal TSH makes hypothyroidism very unlikely. If your symptoms are classic but TSH is normal, explore other causes: anaemia, vitamin D deficiency, sleep disorder, depression.

Myxoedema Coma

A rare, life-threatening complication of severe untreated hypothyroidism — precipitated by illness, surgery, or cold exposure. Presents with profound hypothermia, coma, hypoventilation, and bradycardia. Medical emergency.

How long until levothyroxine works?
Symptoms begin improving within 2–4 weeks, but full normalisation of TSH and symptom resolution takes 6–8 weeks. Some patients feel better within days — others need dose optimisation over months.
Do I have to take levothyroxine forever?
In Hashimoto's hypothyroidism, yes — the thyroid rarely recovers. In transient thyroiditis, T4 may be discontinued after 6–12 months. This is guided by regular TSH monitoring.
Why am I still symptomatic with normal TSH on levothyroxine?
Check: Free T4 (should be in upper half of range), vitamin D, B12, ferritin, depression screen. Some people do better with addition of T3 (liothyronine) — discuss with an endocrinologist.
Can hypothyroidism cause high cholesterol?
Yes. TSH drives lipid metabolism. Hypothyroidism raises LDL and total cholesterol. Cholesterol often normalises with effective thyroid replacement — confirm thyroid is optimally treated before starting statins.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.