What is Prolactin?
💡 Prolactin: normal non-pregnant <500–600 mIU/L (25 ng/mL). Hyperprolactinaemia (>600 mIU/L) suppresses GnRH → anovulation, irregular cycles, galactorrhoea. Causes: pituitary adenoma (prolactinoma), hypothyroidism, drugs (antipsychotics, metoclopramide), stress. Treatment: cabergoline restores ovulation in >85% within 3 months.
Prolactin is a hormone produced by the anterior pituitary gland, primarily responsible for milk production (lactation). In women who are not breastfeeding, elevated prolactin (hyperprolactinaemia) inhibits the hypothalamic-pituitary-ovarian (HPO) axis, causing oligo/anovulation, irregular cycles, and infertility. It is one of the most common and most correctable hormonal causes of female infertility.
🇮🇳 India Context: Prolactin is widely assessed and treated across major Indian fertility centres including Chennai, Mumbai, Bangalore, Delhi, and Hyderabad.
What are the key characteristics of Prolactin?
- Normal range (non-pregnant, non-lactating): <500–600 mIU/L (varies by lab; <25 ng/mL in US units)
- Mildly elevated: 600–1,500 mIU/L — often functional (stress, drugs, hypothyroidism); repeat fasting, morning sample before treating
- Moderately elevated: 1,500–5,000 mIU/L — likely microadenoma or drug cause; MRI pituitary indicated
- Severely elevated: >5,000–6,000 mIU/L — highly likely prolactinoma (pituitary adenoma); MRI mandatory; classify as micro (<10mm) or macro (≥10mm) adenoma
- Mechanism of infertility: elevated prolactin → suppresses GnRH pulsatility → reduced LH/FSH → anovulation/oligo-ovulation → irregular/absent periods
- Galactorrhoea (spontaneous milk production outside lactation): present in ~30–50% of hyperprolactinaemia cases; pathognomonic if bilateral
- Drug causes (very common): antipsychotics (haloperidol, risperidone, metoclopramide), SSRIs (mild elevation), antihypertensives (verapamil, methyldopa), opioids — always take drug history
- Macroprolactin: large molecular form of prolactin (prolactin-IgG complex); causes elevated assay results but is biologically inactive; rule out before treatment; precipitate with polyethylene glycol (PEG)
How does Prolactin work?
Why does Prolactin matter in fertility?
Hyperprolactinaemia is one of the most impactful and most correctable hormonal causes of female infertility. A woman with irregular cycles and infertility who is found to have prolactin of 2,000 mIU/L can frequently achieve a spontaneous natural pregnancy within 3–6 months of starting cabergoline — without IVF. This makes prolactin testing one of the highest-yield investigations in the infertility workup. Clinical errors to avoid: (1) not repeating a mildly elevated prolactin before treating — stress and drug causes are common; (2) not checking TSH alongside prolactin — hypothyroidism is a correctable secondary cause; (3) not testing macroprolactin when prolactin is elevated but the patient is symptom-free — avoids unnecessary treatment; (4) not scanning the pituitary when prolactin is >1,500 mIU/L without drug cause — macroadenomas require neurosurgical assessment if growing.
What are related terms to Prolactin?
FSH (Follicle-Stimulating Hormone)
FSH (Follicle-Stimulating Hormone) is produced by the pituitary gland. In women,…
LH (Luteinizing Hormone)
LH (Luteinizing Hormone) is produced by the pituitary gland. It triggers ovulati…
Ovulation
Ovulation is the release of a mature oocyte (egg) from a dominant ovarian follic…
Menstrual Cycle
The menstrual cycle is a recurring hormonal cycle that prepares the female repro…
TSH (Thyroid-Stimulating Hormone)
TSH (thyroid-stimulating hormone) is secreted by the pituitary gland and regulat…
FAQs about Prolactin
What does high prolactin mean for fertility?
Elevated prolactin (hyperprolactinaemia, >600 mIU/L) suppresses the hypothalamic-pituitary-ovarian axis, reducing or abolishing GnRH pulsatility. This reduces FSH and LH secretion → anovulation or oligo-ovulation → irregular or absent periods → infertility. It is one of the most common correctable hormonal causes of female infertility. With appropriate treatment (cabergoline), ovulation resumes in >85% of women and many conceive naturally.
What causes high prolactin?
Common causes: (1) Prolactinoma: pituitary adenoma — most common pathological cause; micro (<10mm) or macro (≥10mm); treated with cabergoline. (2) Hypothyroidism: elevated TRH stimulates prolactin — check TSH alongside prolactin. (3) Drugs: antipsychotics (haloperidol, risperidone), metoclopramide, SSRIs, antihypertensives, opioids. (4) Stress/needle anxiety: can transiently raise prolactin — always repeat before treating. (5) Macroprolactin: biologically inactive large form — rules out unnecessary treatment.
What is macroprolactin?
Macroprolactin is a large molecular weight form of prolactin (bound to IgG antibody) that is detected by most prolactin immunoassays but is biologically inactive — it does not suppress ovulation. It accounts for elevated prolactin without symptoms in many patients. Ruled out by adding polyethylene glycol (PEG) precipitation step to the assay — if >60% of prolactin precipitates, the result is macroprolactinaemia. These patients do not need treatment.
How is high prolactin treated for fertility?
Dopamine agonists: cabergoline (first line, 0.25–1mg twice weekly) or bromocriptine (older, more side effects). Cabergoline normalises prolactin in >90% and restores ovulation in >85% within 1–3 months. Once ovulation resumes, many women conceive naturally — no IVF needed. If cycles remain irregular after prolactin normalises (3 months), ovulation induction with letrozole is added. Prolactinoma shrinks with cabergoline in most cases — surgery (transsphenoidal) only if drug-resistant macroprolactinoma.
Should I stop cabergoline when pregnant?
For microprolactinoma (the vast majority of cases): cabergoline is stopped when pregnancy is confirmed — the tumour is very unlikely to grow significantly during pregnancy. For macroprolactinoma: discuss with endocrinologist before conception — continued monitoring may be needed. Cabergoline is considered safe in early pregnancy (no increased miscarriage or fetal abnormality risk in registry data), but standard practice is to stop at positive beta-hCG for microprolactinoma cases.
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