Interpretation of Hormone Profiles in Gynaecological Endocrinology
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Direct answer
Interpreting a hormone profile means reading FSH, LH, prolactin, TSH, AMH and androgens together, because each pattern points to a different site of dysfunction. A raised LH with a normal or low FSH suggests PCOS, while a raised prolactin with low gonadotropins suggests a pituitary cause. A raised FSH with low oestradiol indicates ovarian failure. Results must be timed to the cycle, and hormonal contraception can alter them.
What you must remember
- Timing: FSH, LH and oestradiol are usually drawn early in the follicular phase, around days 2 to 3 of the cycle.
- PCOS pattern: A raised LH with normal or low FSH, a raised LH to FSH ratio, raised androgens and raised AMH.
- Hyperprolactinaemia: Raised prolactin with low or normal gonadotropins, causing amenorrhoea or galactorrhoea.
- Primary ovarian insufficiency: A persistently raised FSH, commonly above 25 IU/L on repeat testing, with low oestradiol.
- Hypothyroidism: A raised TSH can raise prolactin and cause anovulation and heavy periods.
- AMH: Reflects ovarian reserve, and is suppressed by combined hormonal contraception.
- Androgen-secreting tumour: Markedly raised testosterone points to an ovarian or adrenal tumour rather than PCOS.
- Hypogonadotropic hypogonadism: Low FSH, LH and oestradiol, pointing to a hypothalamic or pituitary cause.
Matching the hormone pattern to the diagnosis
Each disorder is easier to recognise when it is anchored to one or two hormones that move in a characteristic direction. The table below summarises the typical profile in five common settings.
| Setting | FSH and LH | Prolactin | Key clue |
|---|---|---|---|
| PCOS | LH raised, FSH normal or low | Normal | Raised androgens and AMH |
| Hyperprolactinaemia | Low or normal | Raised | Amenorrhoea, galactorrhoea |
| Primary ovarian insufficiency | FSH and LH raised | Normal | Low oestradiol, age under 40 |
| Hypogonadotropic hypogonadism | Both low | Normal | Low oestradiol, no ovarian failure |
| Hypothyroidism | Usually normal | Raised | Raised TSH, low free T4 |
A practical habit is to read the profile as a checklist: start with prolactin, then the gonadotropins, then the thyroid, and finally the androgens. Each value narrows the differential, and the diagnosis rarely rests on a single result.
Prolactin is best read in a rested, morning sample, since stress and breast stimulation can raise it falsely. Macroprolactin, a large complex that is poorly cleared, can also produce a misleadingly high reading. Thyroid function should be checked in every case of irregular cycles, because thyroid disease is common and treatable.
Where the exam tries to catch you
Most questions in this area test whether the student reads the pattern as a whole rather than one value in isolation.
- Trap: Taking an LH to FSH ratio above 2 as diagnostic of PCOS Correct: The ratio is supportive but not diagnostic, and Rotterdam criteria need two of three features after mimics are excluded.
- Trap: Reading a single high prolactin as a pituitary tumour without repeating it Correct: Stress, drugs such as antipsychotics and metoclopramide, hypothyroidism and macroprolactin must be excluded first.
- Trap: Reading a low AMH on a combined pill as a poor ovarian reserve Correct: Hormonal contraception suppresses AMH, so reserve is best judged off the pill.
Frequently asked questions
What is the classic hormone pattern in polycystic ovary syndrome?
PCOS classically shows a raised LH with a normal or low FSH, giving a raised LH to FSH ratio, along with raised androgens and AMH. The ratio supports the diagnosis but does not establish it. Diagnosis rests on Rotterdam criteria after other causes are excluded.
Which hormone levels suggest primary ovarian insufficiency?
Primary ovarian insufficiency shows a persistently raised FSH, commonly above 25 IU/L on repeat testing, with low oestradiol. It is considered when periods stop before the age of 40. Confirmation on repeat testing is needed before the diagnosis is made.
Why is prolactin measured in a woman with amenorrhoea?
Prolactin is measured in amenorrhoea because hyperprolactinaemia suppresses gonadotropin release and leads to anovulation. Drugs, hypothyroidism and pituitary tumours are the common causes that must be excluded. Galactorrhoea together with a raised prolactin raises suspicion of a prolactinoma.
When should TSH be checked in a woman with irregular menstrual cycles?
TSH should be checked in any woman with irregular menstrual cycles, because both hypothyroidism and hyperthyroidism disrupt ovulation. Hypothyroidism can also raise prolactin and cause heavy menstrual bleeding. Thyroid disease is a common and treatable cause of menstrual disorders.
Why can contraceptive pills change AMH levels?
Combined oral contraceptive pills suppress follicular activity, which lowers AMH levels. A low AMH during pill use therefore does not reliably reflect ovarian reserve. Testing is more reliable when the woman is off hormonal contraception.