Dr. Balaji Chinnaswami and Dr. Nandakumar R, with the help of case discussions, provide quick diagnosis and treatment guides for hypothyroidism and subclinical hypothyroidism (SCH).

---

Case 1- Primary congenital hypothyroidism

A full-term, 2.5 kg, newborn (female) is taken for a heel prick test. TSH was 38 mIU/L (serum units) done on day 3 of life.

Science behind diagnosis

Screening for hypothyroidism is done by TSH in cord blood at birth or heel prick/venous blood sample at 2 to 5 days of life.

• If screening TSH >20 mIU/L of serum units, do a confirmatory venous blood testing
• If in confirmatory venous sample, TSH is >20 mIU/L in first 2 weeks of life or TSH is >10 mIU/L after two weeks of age with low T4 (FT4 <1.17 ng/dl), it is suggestive of primary congenital hypothyroidism

In this case since screening TSH >20 mIU/L, confirmatory venous sample was sent.

Confirmatory venous sample results: TSH- 80 mIU/L and FT4- 0.15 ng/dl. Low T4 and high TSH suggest primary congenital hypothyroidism.

Note: TSH is represented in serum units. If the lab gives results in whole blood units, convert 'whole blood units x 2.2 = serum units'.

Further investigations

• Thyroid ultrasound
• Thyroid nuclear imaging (Technetium 99 scan)

Note:

1. Both investigations are done to look for agenesis of thyroid which needs life-long thyroxine replacement.
2. Treatment should not be delayed if there is delay in getting the imaging done.
3. If not done initially, nuclear scan can be done by 3 years of age.

Advice to give to parents

1. Taking daily treatment is the key to prevent neurological damage. Discuss with parents the importance of compliance and follow up.
2. Crush tablet in small quantity of breast milk. Do not add tablet to bottle feed.
3. Patient should be brought every 3 to 6 months follow up testing of TSH.

Follow-up visit with patient at 8 months: The girl is on 25 µg/day of Tab. Levothyroxine. Her growth appears normal and she has attained developmental milestones appropriately. On follow up testing, FT4 is 1.6 ng/dl (normal 1.1-2.1); TSH is 9.5 mIU/L (normal 0.5-5.5).

Science behind diagnosis

• High TSH in the presence of normal FT4 suggest chronic poor adherence
• TSH is elevated as thyroxine medications were not taken for a long period of time
• FT4 is normal as the girl has been taking multiple doses just before sampling

Treatment and further advice

1. Continue the same dosage of 25 µg/day of thyroxine tablet.
2. Stress the importance of taking medications daily.

---

Case 2- Hypothyroidism in adults

A 36-year old female presents with complaints of weight gain of 3 kgs over 6 months, menstrual disturbance for 5 months, and fatigue for 5 months. She mentioned that her elder sister is also taking treatment for thyroid disorder.

Science behind diagnosis

Females, usually young or middle-aged with clinical features and strong family history gives clues for hypothyroidism.

1. Ask for other symptoms like cold intolerance, constipation, increased sleep, alopoecia etc.
2. Other signs like dry skin, pedal oedema can be elicited
3. The most common aetiology is autoimmune

Investigations

• Thyroid function test- Free T3- low , free T4- low, TSH- elevated (>100 mIU/l). Her blood reports reveal primary hypothyroidism
• USG neck reveal thyroiditis
• Complete blood count reveals anaemia (Haemoglobin- 9.5 g/dl)

Advice to give to patient

1. To follow medicines regularly, motivate the patient to take levothyroxine early in the morning. If a dose is missed, it can be taken any time of the day without skipping.
2. Avoid vegetables like broccoli, cabbage, cauliflower. Minimise gluten-containing diet like wheat, barley, rye, and other grains.
3. Avoid alternate treatments as there are no proven benefits with native medicines.
4. Regularly follow up with doctor, as recommended, as it is needed to decrease or increase dose or even to stop levothyroxine.

---

Case 3- Subclinical hypothyroidism (SCH)

A 56-year-old man presents with his master health check up reports that was done recently. He is a known hypertensive on medications. He doesn’t have any other significant complaints.

Science behind diagnosis

Elevated TSH value with normal free T4 and free T3 reports is suggestive of subclinical hypothyroidism.

• Patients should be asked for associated symptoms if any
• Treatment should be based on thyroid function test, clinical features and thyroid antibody assay

Subclinical hypothyroidism with positive antibody needs to be treated and followed up because of the chance of progression to overt hypothyroidism.

Investigations

• Thyroid function test: F T3 and FT4 are within normal range, TSH- 8.2 mIU/L (elevated)
• Anti-TPO (thyroid peroxidise) antibody >100 IU/ml (elevated ), TgAb (thyroglobulin antibody)- 45 IU/ml (elevated)
• USG neck is normal

Advice to give to patients

1. To follow medicines regularly, motivate the patient to take levothyroxine early in the morning. If a dose is missed, it can be taken any time of the day without skipping.
2. Avoid vegetables like broccoli, cabbage, cauliflower. Minimise gluten-containing diet like wheat, barley, rye, and other grains.
3. Avoid alternate treatments as there are no proven benefits with native medicines.
4. Regularly follow up as recommended by the doctor to check if it is needed to decrease or increase dose or even to stop levothyroxine.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The authors, Dr. Balaji Chinnaswami and Dr. Nandakumar R are professors of Paediatrics and Medicine at a reputed medical college in Chennai.