Hypothyroidism Nursing Guide

Definition & Classification

Hypothyroidism is deficiency of thyroid hormone (T3/T4), characterised by an elevated TSH (in primary disease) and subnormal free T4. It is one of the most common endocrine disorders worldwide and in the GCC region.

Classification

Type	TSH	Free T4	Cause
Primary (most common ~95%)	↑ HIGH	↓ LOW	Thyroid gland failure (Hashimoto's, post-ablation)
Subclinical	↑ HIGH	Normal	Early/compensated; may be asymptomatic
Secondary (pituitary)	↓ LOW or normal	↓ LOW	Pituitary failure (e.g. Sheehan's syndrome)
Tertiary (hypothalamic)	↓ LOW or normal	↓ LOW	TRH deficiency

Key rule: Primary hypothyroidism = HIGH TSH + LOW free T4. Secondary/tertiary = LOW TSH + LOW free T4. TSH is the single best initial screening test.

Symptoms of Hypothyroidism

Symptoms reflect slowed metabolism affecting every system — "everything slows down."

🧊

Cold intolerance

😴

Fatigue, lethargy

⚖️

Weight gain

🐢

Slow HR / Bradycardia

💩

Constipation

🧠

Cognitive slowing

💆

Dry skin, hair loss

🔇

Hoarse voice

🩸

Menorrhagia

💪

Myopathy, cramps

🫁

Pleural/pericardial effusion

🤰

Infertility

Physical Signs

Non-pitting oedema (myxoedema) — periorbital, hands, feet
Dry, coarse skin; coarse hair; loss of lateral eyebrow (Queen Anne's sign)
Bradycardia; low voltage ECG; pericardial effusion
Delayed relaxation of tendon reflexes (hallmark — "hung-up reflexes")
Goitre (in Hashimoto's thyroiditis)
Carpal tunnel syndrome

Causes of Hypothyroidism

Primary (Thyroid)

Hashimoto's thyroiditis — autoimmune; most common cause in iodine-sufficient areas; anti-TPO antibodies positive
Radioactive iodine (RAI) therapy
Thyroidectomy (total or subtotal)
Iodine deficiency (still common in parts of ME)
Drugs: amiodarone, lithium, carbimazole (over-treatment)
Congenital hypothyroidism

Secondary / Tertiary

Pituitary adenoma / surgery
Sheehan's syndrome (postpartum pituitary necrosis)
Cranial radiotherapy
Hypothalamic tumours

Drug-Induced

Amiodarone (contains 37% iodine)
Lithium (blocks thyroid hormone release)
Interferon-alpha, checkpoint inhibitors

Diagnostic Approach

Serum TSH — single best initial test. If elevated → proceed to step 2.

Free T4 — if TSH high + fT4 low = overt primary hypothyroidism. If TSH high + fT4 normal = subclinical hypothyroidism.

Anti-TPO antibodies — positive in Hashimoto's thyroiditis. Useful to confirm autoimmune cause.

Additional bloods — FBC (normocytic/macrocytic anaemia), lipids (dyslipidaemia), CK (myopathy), sodium (hyponatraemia), glucose.

TSH Reference Ranges (approximate)

TSH Level	Interpretation
0.4–4.0 mIU/L	Normal euthyroid
4.1–10 mIU/L	Subclinical hypothyroidism
> 10 mIU/L	Overt hypothyroidism (treat regardless of symptoms)
< 0.4 mIU/L	Suppressed — consider hyperthyroidism or over-replacement

Treatment threshold for subclinical hypothyroidism: Treat if TSH > 10 mIU/L, OR if TSH 4–10 with symptoms, pregnancy, or planning pregnancy.

Associated Lab Abnormalities

Test	Finding in Hypothyroidism
Cholesterol	↑ Total cholesterol, ↑ LDL (hypothyroidism causes dyslipidaemia)
CK (creatine kinase)	↑ Elevated — thyroid myopathy
Sodium	↓ Hyponatraemia (SIADH-like mechanism)
Haemoglobin	↓ Normocytic or macrocytic anaemia (if also B12 deficient — associated autoimmune)
ECG	Bradycardia, low voltage, prolonged QT, flattened T waves

Levothyroxine (T4) Therapy

Levothyroxine (LT4) is the treatment of choice for hypothyroidism. It is a synthetic T4 that is converted to active T3 in peripheral tissues.

Starting Dose

Patient Group	Starting Dose	Rationale
Healthy adults (<50 yrs)	1.6 mcg/kg/day (full replacement)	Can start full dose immediately
Elderly (>65 yrs)	25–50 mcg/day, titrate slowly	Avoid precipitating angina/AF
Ischaemic heart disease	25 mcg/day, titrate very slowly	T4 increases cardiac oxygen demand
Subclinical hypothyroidism	25–50 mcg/day	Often needs lower doses

Administration Instructions (Nurse Education)

Take on empty stomach, 30–60 minutes before breakfast, with water only
Separate from calcium, iron, antacids by at least 4 hours (reduce absorption)
Avoid taking at same time as PPIs, cholestyramine, sucralfate
Do NOT double dose if missed — take as soon as remembered that day; skip if next day
Consistent brand/formulation — bioavailability varies between brands

Monitoring & Titration

Action	Timing
First TSH check after starting/changing dose	6–8 weeks
TSH target (most adults)	0.5–2.5 mIU/L
TSH target in pregnancy	< 2.5 mIU/L (first trimester); < 3.0 mIU/L (2nd/3rd)
Annual monitoring once stable	TSH ± fT4 yearly

Signs of over-replacement (iatrogenic hyperthyroidism): Palpitations, tremor, anxiety, weight loss, AF. Check TSH — if suppressed, reduce dose. Risk of osteoporosis and AF with long-term over-replacement.

In Ramadan: Advise patients to take levothyroxine at Suhoor (pre-dawn meal) — 30–60 minutes before eating. Patients should not skip doses during Ramadan. Remind during Ramadan clinic reviews.

Drug Interactions with Levothyroxine

Drug	Effect	Advice
Calcium supplements	Reduces LT4 absorption	Separate by ≥ 4 hours
Iron supplements	Reduces LT4 absorption	Separate by ≥ 4 hours
Antacids (Al/Mg)	Reduces LT4 absorption	Take LT4 at least 2 hours before
Cholestyramine	Binds LT4 in gut	Separate by ≥ 4–6 hours
Rifampicin, phenytoin	Increases LT4 metabolism	May need higher LT4 dose
Warfarin	LT4 potentiates anticoagulation	Monitor INR closely when dose changes
Amiodarone	Inhibits T4→T3 conversion	Can cause hypo or hyperthyroidism; monitor closely

Myxoedema Coma — Medical Emergency

Myxoedema coma is the most severe, life-threatening presentation of hypothyroidism. Mortality 20–50%. Requires ITU admission.

Clinical Features (SLOWS mnemonic)

Stupor / altered consciousness / coma
Low temperature (hypothermia — core temp < 35°C)
Oedema (periorbital, non-pitting myxoedema)
Weight gain, bradycardia (<60 bpm), low BP
Slow respirations (hypoventilation), hyponatraemia, hypoglycaemia

Precipitating Factors

Infection (most common precipitant)
Cold exposure (relevant in GCC — air conditioning in winter, or exposure during Hajj in cool weather)
Sedatives, opioids, anaesthetic agents
MI, stroke, trauma, surgery
Non-compliance with levothyroxine

Emergency Management

Secure airway — many require intubation due to hypoventilation. High-flow O₂. Attach cardiac monitor.

IV Levothyroxine 200–400 mcg loading dose IV (or oral via NGT if IV not available). Then 1.6 mcg/kg/day maintenance.

IV Hydrocortisone 100mg 8-hourly — must be given BEFORE thyroid hormone (adrenal insufficiency may coexist; giving T4 alone can precipitate adrenal crisis).

Passive rewarming — warm blankets; avoid active external rewarming (causes vasodilatation and cardiovascular collapse). IV warmed fluids.

Correct metabolic abnormalities — IV dextrose for hypoglycaemia, cautious IV saline for hyponatraemia (correct ≤10–12 mmol/L per 24 hrs), mechanical ventilation if CO₂ retaining.

Key point: Give hydrocortisone BEFORE levothyroxine in myxoedema coma. This prevents precipitating an adrenal crisis when thyroid replacement begins, as cortisol metabolism increases with T4.

Hypothyroidism in Pregnancy

Thyroid hormone is critical for fetal brain development, especially in the first 12 weeks before the fetal thyroid is functional. Untreated hypothyroidism = risk of intellectual disability, miscarriage, preterm birth.

Screen all pregnant women with TSH at booking (1st trimester)
TSH target: < 2.5 mIU/L in first trimester; < 3.0 mIU/L in 2nd/3rd trimester
Levothyroxine dose typically increases 25–30% in pregnancy — adjust at confirmed pregnancy
Check TSH every 4 weeks in first trimester, then 8-weekly until stable
Iron and calcium supplements (common in GCC antenatal care) must be separated from LT4 by ≥ 4 hours
Postpartum: dose usually reduced back to pre-pregnancy level

Postpartum thyroiditis: Autoimmune thyroiditis occurring within 12 months postpartum. Presents as transient hyperthyroidism (1–4 months) then hypothyroidism (4–8 months). Often resolves; some become permanently hypothyroid — follow up TSH at 12 months.

GCC-Specific Considerations

Hashimoto's Thyroiditis in GCC Women ▼

Hashimoto's thyroiditis is the most common cause of hypothyroidism in GCC countries, disproportionately affecting women. Family history is important; consanguineous marriages increase prevalence of autoimmune thyroid disease clusters within families. Anti-TPO antibody testing is routine in GCC specialist centres.

Ramadan Fasting with Hypothyroidism ▼

Patients on levothyroxine can fast safely during Ramadan. Recommend taking LT4 at Suhoor (pre-dawn), 30–60 minutes before eating. TSH should be checked before and after Ramadan for patients who change timing or miss doses. Regular fasting does not generally destabilise thyroid replacement if medication is taken consistently.

Iodine Deficiency in the GCC ▼

While coastal GCC countries generally have adequate iodine from seafood, iodine deficiency remains a consideration in some areas and among certain expat populations with restricted diets. The UAE, Saudi Arabia, and other GCC states have iodised salt programmes. Iodine-deficiency goitre (diffuse) remains a cause of hypothyroidism particularly in elderly and rural populations.

Amiodarone-Induced Thyroid Disease ▼

Amiodarone is widely used for AF and ventricular arrhythmias in GCC cardiac centres. It contains 37% iodine by weight and can cause both amiodarone-induced hypothyroidism (AIH) and amiodarone-induced thyrotoxicosis (AIT). Check TSH before starting amiodarone and every 3–6 months during therapy. AIH: treat with levothyroxine. AIT: more complex — may need carbimazole or even thyroidectomy.

MCQ Practice — Hypothyroidism

Q1. A 35-year-old woman has fatigue, weight gain, cold intolerance, and delayed tendon reflexes. TSH is 18 mIU/L and fT4 is low. What is the most likely diagnosis?

A) Subclinical hypothyroidism

B) Overt primary hypothyroidism

C) Secondary hypothyroidism

D) Euthyroid sick syndrome

✅ B — High TSH + low fT4 with symptoms = overt primary hypothyroidism. Subclinical = high TSH + normal fT4. Secondary = low TSH + low fT4.

Q2. A patient with known hypothyroidism presents unconscious with a temperature of 33°C, bradycardia 40 bpm, and hyponatraemia. What must be given BEFORE levothyroxine?

A) IV dextrose 50%

B) IV normal saline 3% (hypertonic)

C) IV hydrocortisone

D) IV liothyronine (T3)

✅ C — In myxoedema coma, IV hydrocortisone must be given BEFORE thyroid hormone replacement to prevent precipitating adrenal crisis (concurrent adrenal insufficiency may be present and T4 replacement increases cortisol metabolism).

Q3. When should levothyroxine be taken for optimal absorption?

A) With breakfast and a glass of milk

B) On an empty stomach, 30–60 minutes before breakfast

C) With the evening meal to improve consistency

D) At the same time as iron supplements to reduce pill burden

✅ B — Levothyroxine absorption is significantly reduced by food, calcium, iron, and antacids. It must be taken on an empty stomach 30–60 minutes before the first meal. Iron must be separated by at least 4 hours.

Q4. A woman with Hashimoto's hypothyroidism is 8 weeks pregnant on levothyroxine 100 mcg/day. Her TSH is 3.8 mIU/L. What is the appropriate action?

A) Maintain current dose as TSH is within normal adult range

B) Reduce dose as pregnancy TSH targets are lower

C) Increase the levothyroxine dose and recheck TSH in 4 weeks

D) Stop levothyroxine — it is contraindicated in pregnancy

✅ C — TSH target in the first trimester is <2.5 mIU/L. TSH of 3.8 is above target. The dose should be increased by approximately 25–30% in pregnancy. Untreated hypothyroidism risks fetal neurodevelopmental harm. Recheck TSH in 4 weeks.

Hypothyroidism — Nursing Guide