Thyroid disorders

The thyroid is a small gland at the front of the neck that sets the pace of metabolism in almost every tissue. It takes up iodine, makes T4 and a smaller quantity of T3, and releases them under instruction from TSH, the signal from the pituitary. The system runs on negative feedback: when thyroid hormone falls, TSH rises to push the gland harder; when hormone is plentiful, TSH falls away. This is why TSH moves first and moves most, and why it is the test that is done first.

Hypothyroidism, an underactive gland, is far the commoner problem in Indian clinics. The usual cause is Hashimoto's thyroiditis, in which the immune system gradually damages thyroid tissue, leaving anti-TPO antibodies as its signature. Because the damage accumulates slowly, symptoms arrive over years and are easily attributed to age, work or motherhood. Subclinical hypothyroidism describes a raised TSH with a normal free T4 — the gland is being pushed harder but is still keeping up. Some of these progress; many do not.

Hyperthyroidism, an overactive gland, is less common. Graves' disease, an autoimmune condition in which antibodies stimulate rather than damage the gland, accounts for most of it, sometimes with eye involvement. A single autonomously overactive nodule can do the same. Thyroiditis behaves differently again: inflammation releases stored hormone in a burst, producing weeks of overactivity followed by a period of underactivity and often full recovery. Postpartum thyroiditis follows exactly that pattern in a small percentage of women after delivery and is regularly mistaken for anxiety or exhaustion.

The Indian picture has its own texture. Universal salt iodisation transformed a country once marked by widespread goitre, yet pockets of deficiency persist in some inland and hill districts even as urban intake is ample. The widely cited eight-city Indian study reported hypothyroidism in roughly one adult in ten, most of it subclinical, anti-TPO antibodies in around one in five, and higher rates inland than on the coast. Thyroid disease is several times more common in women. Set against that, thyroid tests now appear in almost every health package sold here — which finds real disease, and also generates a large volume of mildly abnormal numbers that get treated rather than repeated.

ⓘThis information is educational and not a diagnosis.

Underactivity slows things down. Tiredness that sleep does not repair, intolerance of cold, dry skin and coarse hair, thinning at the scalp and outer eyebrows, puffiness around the eyes, a slowed pulse, low mood and mental sluggishness, heavier or irregular periods, muscle aches, and hoarseness. Constipation belongs firmly on that list — slowed gut transit is a genuine feature of hypothyroidism, and thyroid function is a standard check when bowel habit has changed without explanation. Weight gain is usually modest, and much of it is fluid — enough to be experienced as weight arriving without a change in eating, rarely enough to account for a large gain on its own.

Overactivity speeds things up. Palpitations, a rapid or irregular pulse, weight loss despite good appetite, heat intolerance and sweating, tremor, anxiety and restlessness, loose stools, disturbed sleep, and lighter or absent periods. In Graves' disease the eyes may protrude, feel gritty or water; in older people the picture can be quieter, appearing as atrial fibrillation or unexplained weight loss alone.

One association deserves mention. Autoimmune thyroid disease travels with other autoimmune conditions, and pernicious anaemia is among the commonest — which is why B12 deficiency is worth checking in someone with Hashimoto's who remains tired despite a normal TSH, particularly in vegetarian households where dietary B12 is already low. Coeliac disease and type 1 diabetes cluster in the same way.

A goitre, or a nodule felt in the neck or found on a scan done for something else, is common and usually benign. Nodules are found on ultrasound in a large fraction of adults, and only a small minority prove to be cancer — worth knowing, because a nodule report generates a great deal of anxiety.

The signs listed below are of a different order and need prompt assessment rather than the next convenient appointment.

TSH is first-line because the feedback loop amplifies it: a modest fall in thyroid hormone produces a proportionally much larger rise in TSH, so TSH detects change earlier than measuring the hormone itself. Free T4 is added when TSH is abnormal, because the pair together distinguish overt disease from the subclinical pattern, and because in the rare pituitary disorders TSH alone misleads.

Several things confuse interpretation, and knowing them prevents unnecessary treatment. TSH follows a daily rhythm, running highest in the late night and early morning and lower in the afternoon, so sampling time shifts the number. It rises transiently after acute illness and falls during it — the non-thyroidal illness pattern — which is why testing during or just after a significant illness is unhelpful. Reference ranges differ between laboratories and between assay platforms, so results from two labs are not directly comparable. And high-dose biotin, sold widely for hair and skin and taken by a great many people in India without mentioning it, interferes with common immunoassays and can produce a picture that looks convincingly like Graves' disease. Stopping biotin for a few days before testing resolves it.

There is a genuine, unsettled debate about where the upper limit of normal sits. Most Indian laboratories report up to around 4.0 to 4.5 mIU/L; some argue the true upper limit in a healthy population is nearer 2.5, and others that the range widens legitimately with age. Pregnancy is different again — lower trimester-specific limits are used, guidance has shifted over the last decade, and this genuinely matters, because untreated hypothyroidism in pregnancy affects outcomes.

The practical consequence: a single mildly raised TSH is information, not a diagnosis. A repeat with free T4 after six to twelve weeks, with anti-TPO antibodies checked once, resolves most of these. Free T3 has a place in suspected overactivity. Reverse T3 and repeated antibody titres are commonly added to Indian health packages and rarely change what is done.

Where the gland is enlarged or a nodule is present, ultrasound describes size and features and grades risk by TIRADS; fine needle aspiration is reserved for nodules whose features and size warrant it. A radioiodine uptake scan helps separate Graves' disease from thyroiditis when hormone levels are high.

Cost and access shape what happens in practice. A TSH at a chain laboratory is inexpensive and available almost everywhere; a full profile with antibodies costs several times as much, and ultrasound and FNAC are concentrated in larger towns. That gradient explains two familiar patterns: over-testing in cities, where wide panels arrive in packages nobody ordered deliberately, and under-testing elsewhere, where a woman with years of fatigue has had no TSH at all. It also explains levothyroxine bought across the counter on a relative's old prescription — the tablet is cheap, and the monitoring that makes it safe is what gets skipped.

Hypothyroidism is treated by replacing what the gland is not making. Levothyroxine is synthetic T4, identical to the body's own, and the body converts it to T3 as required.

Absorption is the part worth understanding well. Levothyroxine is taken with water on an empty stomach, with a gap before tea, coffee or breakfast — coffee in particular reduces absorption noticeably. Calcium and iron supplements, both very common in Indian households, bind it in the gut and are usually separated by several hours, as are antacids and proton pump inhibitors. Bedtime dosing, well after the last meal, suits some people better. Consistency matters more than the routine chosen.

Dose is individualised to body weight, age, heart disease and pregnancy, and adjusted on a repeat TSH after six to eight weeks, since the level takes that long to settle. Changing dose on symptoms alone, or on a report taken too soon, produces a swinging TSH. Any change is a prescriber's decision, not something to adjust between visits.

Whether to treat subclinical hypothyroidism is judged case by case, weighing the TSH level, antibody status, symptoms, age, cardiovascular risk and pregnancy plans. Combination T3 and T4 therapy, and desiccated thyroid extract, are asked about constantly; trials have not shown consistent superiority over levothyroxine alone, extract preparations vary between batches, and a minority of people nonetheless report feeling better on them. That is an honest summary of an unresolved question, and it belongs in a specialist conversation.

Hyperthyroidism has three established approaches: anti-thyroid drugs such as carbimazole or methimazole, which reduce hormone production and require monitoring of blood counts and liver tests; radioactive iodine, which reduces the gland over months and frequently leads to hypothyroidism afterwards; and surgery, where the gland is very large, compressive, or where other approaches are unsuitable. Beta blockers ease palpitations and tremor while the underlying treatment takes effect. Choice depends on cause, age, severity, eye involvement and pregnancy plans. Thyroid storm — high fever, a very fast pulse, agitation or confusion — is a medical emergency.

Nodules are mostly watched rather than treated. Those benign on FNAC are followed with ultrasound; suspicious ones go to surgery. Reassurance here is genuinely earned by the numbers.

Everyday questions. Iodised salt is worth keeping. Selenium and iodine supplements have no established role in ordinary Indian diets and do harm in excess. Goitrogenic vegetables in normal portions are fine. Correcting iron, B12 and vitamin D deficiency often helps residual tiredness when TSH is already in range.

Most of the confusion around thyroid disease comes from the reports rather than the illness — three numbers, several reference ranges, and a great deal of advice attached to them. Understanding what TSH measures, why it moves so much, and why a single value is read alongside the story rather than on its own, changes what happens next.

The Learning Session below works through reading blood reports in a small group, thyroid among them, with time for questions.

If you have thyroid reports from different laboratories and different years, and want them read together as one picture, that is a conversation for a consultation rather than an article.