Thyroid Disorders: Reading Your TSH, Symptoms and Treatment of Under- and Over-active Thyroid, and Why Thyroid Tests Often Look "Odd" in CKD

What the thyroid does

The thyroid, at the front of the neck, secretes thyroxine (T4) and triiodothyronine (T3), which set the body's metabolic rate — heart rate, temperature, gut motility, energy use and cholesterol metabolism all depend on it. The pituitary releases TSH (thyroid-stimulating hormone) to direct the gland: too little thyroid hormone → TSH rises; too much → TSH falls [1][2].

Thyroid disease affects about 200 million people. Hypothyroidism (including subclinical) affects about 4–5%, hyperthyroidism 1–2%; women are affected 5–8 times more than men, and prevalence rises with age [1][2].

Reading your TSH

TSH is the most sensitive first-line test; if abnormal, free T4 (± T3) is added [1][2]:

TSH has a diurnal rhythm (higher in early morning), different pregnancy ranges (first-trimester upper limit ≈2.5), and the upper limit of normal rises to 6–7 over age 60 (ETA suggests not treating asymptomatic older adults with TSH 7–10) [3]. A single abnormal result should be repeated after 4–12 weeks; 30–60% of subclinical abnormalities normalise spontaneously [1][3].

Hypothyroidism: symptoms and treatment

Symptoms (slow onset, easily attributed to other causes): fatigue, cold intolerance, weight gain, constipation, dry skin, hair loss, poor memory, low mood, heavy periods, slow pulse, raised cholesterol [1]. The commonest cause is Hashimoto's thyroiditis (autoimmune, anti-TPO positive).

Overt hypothyroidism (high TSH + low free T4) is always treated: levothyroxine (LT4) [1].

Subclinical hypothyroidism (high TSH, normal free T4) — treat or not? ATA/ETA [1][3]:

• TSH ≥10: treatment recommended (higher cardiovascular risk and progression to overt disease).
• TSH 4–10: a trial of treatment if symptomatic, anti-TPO positive, pregnant or planning pregnancy, or <65 with cardiovascular risk; most asymptomatic people over 65–70 do not need treatment (TRUST trial showed no benefit) [3][4].

Levothyroxine practicalities [1]:

• Take on an empty stomach (30–60 min before breakfast, or at bedtime 3–4 h after dinner), ≥4 hours apart from calcium, iron, phosphate binders, antacids and coffee — especially relevant for kidney patients on binders and calcium.
• Starting dose: full replacement (≈1.6 µg/kg/day) in young healthy adults; start at 25–50 µg if over 60 or with heart disease, adjusting every 6–8 weeks by TSH.
• Target: TSH within the normal range (usually 0.5–4.0; slightly higher acceptable in older adults). Once stable, check every 6–12 months.
• Re-check after brand changes, pregnancy, or starting oestrogen, anti-epileptics or certain anti-rejection drugs.

Hyperthyroidism: symptoms and three treatments

Symptoms: palpitations, tremor, heat intolerance, sweating, weight loss despite increased appetite, anxiety, insomnia, diarrhoea, lighter periods, bulging eyes (specific to Graves' disease) [2]. The commonest cause is Graves' disease (autoimmune, TSH-receptor antibody positive), then toxic nodular goitre.

Three treatment options [2]:

Beta-blockers (propranolol, atenolol) control palpitations and tremor while other treatments take effect [2].

Subclinical hyperthyroidism (TSH <0.1) in older adults raises atrial fibrillation and osteoporosis risk and is often treated [2].

CKD: why thyroid tests often look "odd"

A common but rarely explained experience for kidney patients [5]:

1. Non-thyroidal illness (low T3 syndrome): CKD, especially dialysis, often shows low T3, normal or slightly low free T4 and normal TSH — an adaptation to chronic illness, not hypothyroidism, and not an indication for thyroid hormone. Replacing it may be harmful.
2. TSH may be mildly raised: slower TSH clearance and a blunted response to TRH mean mild elevation (4–10) is more common (≈20% of dialysis patients); be more conservative in diagnosing subclinical hypothyroidism — repeat, and weigh symptoms and antibodies.
3. True hypothyroidism is also more common in CKD (about twice the general population), possibly from iodine retention, autoimmunity, or loss of binding proteins in nephrotic syndrome.
4. Hypothyroidism makes eGFR look worse: low thyroid hormone → reduced renal blood flow and GFR → higher creatinine; eGFR can improve after replacement. A new fall in kidney function with hypothyroid symptoms warrants a TSH.
5. Amiodarone (an antiarrhythmic) contains large amounts of iodine and can cause hypo- or hyperthyroidism; check thyroid function every 6 months.
6. Iodinated contrast can transiently affect thyroid function, especially with nodules.
7. Transplant: some mTOR inhibitors may affect thyroid function; levothyroxine has no major interaction with anti-rejection drugs, but must be separated from phosphate binders, calcium and iron.

When to seek care

Urgently: fever, sore throat or mouth ulcers while on antithyroid drugs (possible agranulocytosis); heart rate >140 with fever, agitation or confusion (thyroid storm); extreme drowsiness, hypothermia and confusion (myxoedema coma, rare).

Routine appointment: a neck lump or a sensation of something in the throat when swallowing; unexplained weight change, palpitations or temperature intolerance; a sudden rise in cholesterol; pregnancy or planned pregnancy with a thyroid history; unexplained fatigue and swelling in CKD.

Questions to ask your doctor

1. What are my TSH and free T4? Should they be repeated?
2. Given my age (and kidney function), does my subclinical hypothyroidism need treatment?
3. When should I take levothyroxine, and how do I separate it from my phosphate binder and calcium?
4. Could my declining kidney function be related to my thyroid?
5. (Hyperthyroidism) Which of the three treatments suits me, and what warning signs should I watch for?

References

1. Jonklaas J, et al. Guidelines for the Treatment of Hypothyroidism (ATA). Thyroid. 2014;24(12):1670–1751. https://doi.org/10.1089/thy.2014.0028
2. Ross DS, et al. 2016 ATA Guidelines for Diagnosis and Management of Hyperthyroidism. Thyroid. 2016;26(10):1343–1421. https://doi.org/10.1089/thy.2016.0229
3. Pearce SH, et al. 2013 ETA Guideline: Management of Subclinical Hypothyroidism. Eur Thyroid J. 2013;2(4):215–228. https://doi.org/10.1159/000356507
4. Stott DJ, et al. TRUST. N Engl J Med. 2017;376(26):2534–2544. https://doi.org/10.1056/NEJMoa1603825
5. Rhee CM. The interaction between thyroid and kidney disease. Curr Opin Endocrinol Diabetes Obes. 2016;23(5):407–415. https://doi.org/10.1097/MED.0000000000000275 ; Narasaki Y, Sohn P, Rhee CM. The Interplay Between Thyroid Dysfunction and Kidney Disease. Semin Nephrol. 2021;41(2):133–143. https://doi.org/10.1016/j.semnephrol.2021.03.008

This article compiles publicly available medical information for educational purposes only. It is not medical advice and has not been reviewed by a practising physician. For any health or medication question, consult a qualified professional. For chest pain, sudden breathlessness, one-sided weakness or slurred speech, call your local emergency number or go to the emergency department immediately.