The major hormone systems and their tests
| Gland / System | Key Hormones | Primary Blood Tests |
|---|---|---|
| Thyroid | T3, T4, Calcitonin | TSH, free T4, free T3, anti-TPO, TRAb |
| Pituitary | TSH, FSH, LH, ACTH, Prolactin, GH | Prolactin, LH, FSH, ACTH, IGF-1 |
| Adrenal cortex | Cortisol, Aldosterone, DHEA | Morning cortisol, aldosterone:renin ratio, DHEA-S |
| Adrenal medulla | Adrenaline, Noradrenaline | Plasma metanephrines (for phaeochromocytoma) |
| Pancreas | Insulin, Glucagon | Fasting insulin, fasting glucose, C-peptide, HbA1c |
| Gonads (women) | Oestrogen, Progesterone, AMH | Oestradiol, FSH, LH, progesterone, AMH, prolactin |
| Gonads (men) | Testosterone | Total testosterone, free testosterone, LH, FSH, SHBG |
| Parathyroid | PTH | PTH, calcium, phosphate, vitamin D |
When to test hormones — timing matters
| Hormone | Best time to test | Why |
|---|---|---|
| Cortisol | 8–9am (peak) | Cortisol follows a strong diurnal rhythm |
| Testosterone | 7–10am | Peaks in the morning |
| Progesterone | Day 21 of a 28-day cycle (7 days after ovulation) | Confirms ovulation |
| FSH/LH (women) | Day 2–3 of cycle | Basal level; checks ovarian reserve and pituitary |
| TSH | Any time — fasting not required | Consistent throughout the day |
| Fasting insulin | After 8–12 hours fasting | Requires fasting |
| Aldosterone:renin ratio | Morning, after sitting quietly 15 min | Avoid diuretics 4 weeks before |
Recognising hormonal imbalance patterns
Fatigue + weight gain + cold intolerance + constipation = check TSH
This is the classic hypothyroid constellation. TSH is always the first test.
Unexplained weight gain + irregular periods + acne + hair growth = check testosterone, LH:FSH ratio, insulin
PCOS (polycystic ovary syndrome) typically shows high LH:FSH ratio, elevated testosterone, and high fasting insulin from insulin resistance.
Fatigue + weight loss + low blood pressure + skin darkening = check morning cortisol + ACTH
These features suggest Addison disease (adrenal insufficiency). A morning cortisol below 5 mcg/dL is strongly suggestive; a short Synacthen test confirms.
High blood pressure + low potassium + fatigue = check aldosterone:renin ratio
This triad suggests primary hyperaldosteronism (Conn syndrome) — the most common secondary cause of hypertension. ARR >30 is suspicious; adrenal CT and adrenal vein sampling follow.
Episodic hypertension + palpitations + headache + sweating = check plasma metanephrines
This classic triad suggests phaeochromocytoma — a rare adrenal medulla tumour. Plasma metanephrines are the most sensitive test. Never biopsy an adrenal mass before excluding phaeochromocytoma.
Questions to ask your doctor
- Should I test hormones in the morning?
- Is my fatigue from thyroid, adrenal or sex hormone imbalance?
- Do I need a stimulation test (Synacthen test) for adrenal function?
- Could a pituitary problem be causing my hormone imbalance?
- Should I see an endocrinologist?
Medical Disclaimer: This page is for general educational purposes only and does not constitute medical advice. Always consult a qualified doctor for diagnosis and treatment.