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Biomarker reference

Hormones & thyroid

Thyroid, cortisol rhythm and sex hormones, tuned to how you actually move through a day, not just to a reference range.

Hormone markers describe the signalling systems that set energy, mood, sleep and recovery, and thyroid function is where most investigations start. TSH is the standard screening test and a genuinely good one — the pituitary responds to small changes in thyroid output before thyroid hormone levels themselves leave the reference range, which makes TSH the most sensitive single indicator of thyroid dysfunction. Its limitation is that it measures the signal rather than the hormone. It cannot show whether T4 is being converted to active T3, whether an autoimmune process is underway, or whether conversion is being suppressed by illness or chronic stress. Those require free T4, free T3, reverse T3 and thyroid antibodies. Thyroid disorders and autoimmune thyroiditis are common in India and disproportionately affect women, which makes the distinction between screening and understanding a practical one.

01

Why are these markers read together?

No marker in this group means much on its own. Hormones & thyroid covers 19 of the measurements in the Peak Brain panel, and a physician reads them as a pattern — one value at the edge of a reference range means something quite different depending on what the others are doing.

  • TSH, free T4 and free T3 describe three different steps — the signal, the reserve and the active hormone — and a problem can sit at any one of them while the others read normal.
  • Thyroid antibodies frequently turn positive years before TSH shifts, so an autoimmune process can be underway while every screening test still looks unremarkable.
  • Thyroid symptoms overlap almost completely with iron and B12 deficiency. Reading TSH alongside ferritin and B12 is what prevents attributing fatigue to the thyroid when it belongs elsewhere.
02

What does this group explain?

  • Fatigue, cold intolerance and weight change that a single TSH result has failed to account for.
  • Whether thyroid symptoms in the presence of a normal TSH reflect a conversion problem, an autoimmune process, or a different cause entirely.
  • How cortisol rhythm and sex hormones interact with thyroid function to produce a pattern no single hormone explains.
03

Hormones & thyroid: marker explanations

TSH

TSH is the signal the pituitary gland sends to instruct the thyroid to produce hormone, and it moves in the opposite direction to thyroid output.

04

Also measured in this group

These markers are included in the panel and read alongside the ones above. They have no standalone reference page, because outside the context of a full panel there is little useful to say about them individually — and a page that exists only to fill a URL is worse than no page.

  • Free T3the active hormone
  • Free T4the reserve
  • Total T3bound and free
  • Total T4bound and free
  • Reverse T3conversion under stress
  • Anti-TPO antibodiesautoimmune thyroid
  • Anti-thyroglobulinthe second antibody
  • Morning cortisolhow you start the day
  • Evening cortisolwhy you are wired at 11pm
  • DHEA-Sadrenal reserve
  • Total testosteronedrive and recovery
  • Free testosteronewhat is actually available
  • SHBGwhat binds it up
  • Estradiolcycle and mood context
  • Progesteronecycle phase context
  • LHpituitary drive
  • FSHreserve and cycle
  • Prolactinstress and pituitary load
05

Who reviews this group

Reviewer assignment follows speciality. Pages in this group are assigned to Dr. Alfia Kaki (MD, PGC), and each page carries a byline naming its reviewer and the date of review.

  • Dr. Alfia Kaki Internal Medicine, Rheumatic & Musculoskeletal Medicine

Hormones & thyroid: common questions

My TSH is normal but I have hypothyroid symptoms. What next?

TSH measures the pituitary signal, not thyroid hormone. Free T4 and free T3 show what is actually being produced and converted, reverse T3 indicates whether conversion is being suppressed, and anti-TPO antibodies reveal an autoimmune process that can precede any TSH change by years. Those are the markers that explain a normal TSH alongside real symptoms.

Does the time of day matter for thyroid testing?

Yes. TSH follows a daily rhythm, peaking overnight and bottoming in the late afternoon, and the swing is enough to move a borderline result across a threshold. Consistent morning sampling makes results comparable to each other over time.

Are thyroid problems more common in India?

Thyroid disorders, and autoimmune thyroiditis in particular, are common in Indian populations and affect women disproportionately. Widespread iron and B12 deficiency compound the picture, because they produce overlapping symptoms and because iron status affects thyroid hormone synthesis.

The programme

One marker rarely answers the question.

Peak Brain draws a full blood and urine panel at your home, has a licensed physician read every marker together rather than one at a time, and turns what they find into a ranked 90-day protocol with a retest at the end.

How the programme works