Guide
Endocrine tests and examinations: a guide
Short answer
The endocrinologist decides which tests are needed after the examination. This guide explains what the most commonly requested tests show and how to prepare for some of them. Reference ranges depend on the laboratory. Always interpret the result together with your doctor.
The doctor decides which tests you need after the examination.
| Test / examination | What it shows | Preparation and the doctor's notes |
|---|---|---|
| Fasting blood sugar | Sugar metabolism | ≥8 hours of fasting. ≥126 mg/dL (7 mmol/L) is one of the criteria for diabetes. The doctor's practical threshold: 100 mg/dL and above is a warning sign; if it is 110 mg/dL (6.1 mmol/L) or above, do not decide on your own — see an endocrinologist. If you have symptoms of diabetes, the first step is to have your fasting blood sugar checked. |
| HbA1c (3-month average sugar) | How well sugar has been controlled over the last 3 months | It does not matter whether you are fasting or have eaten. Prediabetes: 5.7–6.4%; diabetes: ≥6.5% (48 mmol/mol). In people with diabetes, the general target is often <7%; in pregnant women and some other groups, it is kept lower. The test may not give an accurate result in people with a hemoglobin disorder. The doctor's practical note: 5.5–6% is a warning sign, and 6% and above is the time to see a doctor. |
| Glucose tolerance test (OGTT) | Glucose tolerance | At the 2-hour mark, ≥200 mg/dL (11.1 mmol/L) is a criterion for diabetes. |
| Fasting insulin and HOMA-IR | Insulin resistance | Taken after 8–10 hours of fasting. HOMA-IR = fasting sugar (mg/dL) × fasting insulin / 405. The threshold the doctor uses: above 2.5. Example: with sugar at 85 mg/dL (normal) and insulin at 18 → 85 × 18 / 405 = 3.8. In other words, a normal fasting sugar does not mean the metabolism is normal. Normal insulin values are roughly in the range of 2–25 (depends on the laboratory). |
| TSH | The pituitary hormone that “makes the thyroid work” | The normal range is often 0.27–4.2, but it varies by laboratory. There are special target ranges depending on age, symptoms and pregnancy. A high TSH does not always mean a permanent disease — the cause needs to be investigated. |
| Free T4 (FT4), free T3 (FT3) | Thyroid hormones | The degree of hypothyroidism and hyperthyroidism; in subacute thyroiditis, TSH is low and FT4 and FT3 are high. |
| Anti-TPO, anti-Tg | Markers of an autoimmune process in the thyroid (Hashimoto's, etc.) | If it has come out high once, it is not checked again and again: it establishes the diagnosis but does not change the course of treatment (video). |
| Prolactin | Pituitary hormone | It should be taken at least 2 hours after waking up and when you are not under stress. Normal: up to about 20 ng/mL in men and up to 25 ng/mL in women (depends on the laboratory). |
| AMH | Ovarian reserve in women, testicular reserve in men | Normal values are often in the range of 2–5 ng/mL (depends on the laboratory and age). It rises in PCOS and falls as menopause approaches. |
| Cortisol | The “stress hormone” of the adrenal glands | If an excess (Cushing's syndrome) or a deficiency (Addison's disease) is suspected, it is checked with special tests. |
| GH (growth hormone), IGF-1 | Acromegaly, growth hormone deficiency | When needed, together with challenge tests and an MRI of the pituitary. |
| Calcium, phosphorus, PTH, creatinine | Parathyroid and bone-mineral metabolism | In a parathyroid adenoma, calcium and PTH are high. |
| 25(OH) vitamin D | Vitamin D reserves | The vitamin D dose is set according to the blood level. If poisoning is suspected, it is checked together with calcium, phosphorus and creatinine. |
| Lipid profile | Cholesterol (LDL, HDL), triglycerides | Cardiovascular risk; endocrine causes (thyroid, insulin resistance) are taken into account. |
| Vitamin B12 | Nervous system, blood | It should be checked from time to time in people who have been taking metformin for a long time. |
| ESR, CRP | Inflammation | When subacute thyroiditis is suspected. |
| Thyroid and neck ultrasound | Structure of the gland, nodules, cysts, lymph nodes | See: Thyroid and neck ultrasound |
| Thyroid FNA | Cytological characteristics of the nodule | See: Thyroid FNA (fine-needle biopsy) |
| Scintigraphy | Whether a nodule is “hot” (active) or “cold”; the location of a parathyroid adenoma | Used to confirm a toxic adenoma and a parathyroid adenoma. For the parathyroid, it is used together with ultrasound and PTH washout. |
| Densitometry (bone density) | Osteoporosis, fracture risk | For diagnosis, for assessing the need for medication, and for monitoring treatment. The T-score result is interpreted together with symptoms and blood tests. |
| X-ray of the left wrist (bone age) | A child's bone development | When slow height growth or early or delayed puberty is suspected. In any case, the X-ray should be taken and interpreted under a doctor's supervision. |
| Pituitary MRI | Prolactinoma, acromegaly | When high prolactin or excess growth hormone is suspected. |