TSH (Thyroid-Stimulating Hormone)

Hormones

Thyroid Panel

TSH (Thyroid-Stimulating Hormone) is the pituitary's signal to the thyroid, telling it how much hormone to produce. It is the primary screening marker for thyroid dysfunction because it responds sensitively to changes in thyroid output. A longevity practice tracks it as the first line in assessing thyroid health, which underpins metabolism, energy, and cognition.

What It Measures

Pituitary signal to thyroid; primary screening marker for thyroid dysfunction

Optimal vs. Lab Range

Longevity Optimal

1.0–2.5 mIU/L

Target range for optimal health and longevity based on research.

Standard Lab

0.45–4.5 mIU/L

Population-based reference range from standard labs.

Why It Matters

TSH works on a feedback loop, so its value moves opposite to thyroid activity. A high TSH indicates the thyroid is underproducing, as in hypothyroidism, iodine deficiency, or Hashimoto thyroiditis, and can bring fatigue, weight gain, and cognitive slowing. A low TSH suggests overproduction, as in hyperthyroidism, Graves disease, or, less commonly, pituitary insufficiency. Because TSH reflects signaling rather than the hormones themselves, it is most informative when paired with Free T4, Free T3, and reverse T3, and with the antibody markers TPO and TG. Together these clarify whether thyroid function, conversion, or autoimmunity is driving symptoms relevant to long-term health.

When Low

Hyperthyroidism (low TSH = thyroid overproducing), Graves disease, pituitary insufficiency

When High

Hypothyroidism (high TSH = thyroid underproducing), iodine deficiency, Hashimoto thyroiditis

How to Optimize

When TSH indicates true hypothyroidism, physician-directed thyroid medication is titrated to the individual and monitored, and correcting iodine deficiency helps where present. Nutrients such as selenium and zinc support thyroid function and hormone conversion. Because TSH is a signal rather than the active hormone, treatment decisions rest on the whole panel and symptoms. Hormone testing and treatment must be individualized with your physician; this content is educational and not a substitute for medical advice.

Key Interventions & Linked Compounds

Strong evidence

Key Interventions

Thyroid medication (clinical)

iodine (if deficient)

selenium

zinc

Linked Compounds & Supplements

Selenium

Zinc

Iodine

Ashwagandha

L-tyrosine

Curated from clinical literature. Individual results vary; consult a qualified clinician before changing a protocol.

Ordering Notes

Specimen

Serum; saliva for diurnal cortisol panels

Patient prep

No fasting required. Maintain usual diet and medications unless advised.

Recommended cadence

Semi-annual

Reporting unit

Confirm with the performing lab — units vary by region.

Pre-analytic notes

Standardize draw time of day, hydration, and recent exercise. Note any acute illness, supplements, or hormonal therapies on the requisition.

Recommended Follow-Up Actions

1
Confirm the result is reliable
Repeat abnormal values before acting — preferably from the same lab, same time of day, and under consistent prep. Rule out acute illness, recent intense exercise, or medication effects that can shift TSH (Thyroid-Stimulating Hormone).
2
Compare against optimal, not just lab range
Use the optimal window above as the target. Lab "normal" is built from the general population and often misses early dysfunction.
3
Pair with related markers
Order a complementary panel covering metabolic, inflammatory, and hormonal context to interpret this marker properly.
4
Discuss interventions with a clinician
Use the interpretation guidance above to frame the conversation. Bring trends, not just one datapoint, to your visit.
5
Re-test on a defined cadence
If a change is implemented, re-measure in 8–12 weeks for fast-moving markers, or 3–6 months for slower ones, to confirm response before escalating.