Hyperprolactinemia: Definition & Physiology - Milky Messengers
- Definition: Persistently elevated serum prolactin (PRL) levels.
- Normal PRL: <25 ng/mL (non-pregnant women), <20 ng/mL (men).
- Source: Lactotroph cells in the anterior pituitary gland.
- Primary Functions:
- Induces & maintains lactation (milk production).
- Breast development (mammogenesis).
- Regulation:
- Predominantly inhibitory control by dopamine from hypothalamus.
- Stimulatory factors: TRH, estrogen, suckling, serotonin.
⭐ Dopamine is the primary physiological inhibitor of prolactin secretion from the anterior pituitary.
Etiology of Hyperprolactinemia - Prolactin's Partners in Crime
| Category | Causes |
|---|---|
| Physiological | Pregnancy, lactation, stress, sleep, nipple stimulation, exercise |
| Pathological | Prolactinoma (PRL >200 ng/mL highly suggestive), other pituitary tumors (stalk compression), primary hypothyroidism (↑TRH), CKD, cirrhosis, PCOS, chest wall trauma |
| Pharmacological | 📌 DAMA: Dopamine antagonists (e.g., phenothiazines, haloperidol, metoclopramide, domperidone), Antihypertensives (e.g., methyldopa, verapamil, reserpine), Many psychotropics (TCAs, SSRIs, MAOIs), Acid blockers (cimetidine), Estrogens, Opiates |
Clinical Features of Hyperprolactinemia - Telltale Signs & Symptoms
| Females | Males |
|---|---|
| * Oligomenorrhea / Amenorrhea | * Decreased libido |
| * Galactorrhea (non-puerperal milk) | * Erectile dysfunction |
| * Infertility (anovulation) | * Infertility (oligospermia, asthenospermia) |
| * Decreased libido | * Gynecomastia |
| * Dyspareunia (vaginal dryness) | * Galactorrhea (rare) |
| * Bone loss (long-term estrogen deficiency) | * Visual field defects (e.g., bitemporal hemianopia if pituitary macroadenoma) |
| * Headaches (if tumor) |
Diagnosis & Investigations in Hyperprolactinemia - Unmasking the Culprit
- Initial Tests:
- Serum prolactin (repeat if mild ↑). Levels:
- 25-100 ng/mL: Various causes.
- >100 ng/mL: Suspect prolactinoma.
- >200-250 ng/mL: Highly indicative.
- TSH, RFTs, β-hCG.
- Serum prolactin (repeat if mild ↑). Levels:
- Hook Effect: Suspect with very large tumors & moderately ↑ prolactin; dilute sample.
⭐ Pituitary MRI (sellar MRI) is the imaging modality of choice when prolactin levels are significantly elevated (e.g., >100 ng/mL) or a tumor is suspected, to look for microadenoma (<1cm) or macroadenoma (≥1cm).
Management of Hyperprolactinemia - Taming the Tide
Goals: Normalize prolactin, restore gonadal function, ↓ tumor size, alleviate symptoms.
- Treat cause: Stop offending drugs, manage hypothyroidism.
- Prolactinomas:
- Dopamine Agonists (DA): 1st line.
- Cabergoline (preferred): Start 0.25-0.5 mg weekly.
- Bromocriptine: Start 1.25-2.5 mg daily.
- Surgery (Transsphenoidal): For DA resistance/intolerance, or visual defects not improving with DA.
- Radiotherapy: Rare.
- Dopamine Agonists (DA): 1st line.
- Asymptomatic microprolactinoma: Observation.
⭐ Dopamine agonists (e.g., Cabergoline, Bromocriptine) are the first-line medical treatment for symptomatic prolactinomas, effective in normalizing prolactin and shrinking tumor size.
High-Yield Points - ⚡ Biggest Takeaways
- Prolactinomas are the most common cause; drug-induced (antipsychotics, metoclopramide) is also frequent.
- Presents as galactorrhea, amenorrhea (females), ↓ libido, infertility, and gynecomastia (males).
- Prolactin levels > 200 ng/mL strongly suggest prolactinoma; levels 25-100 ng/mL can be due to various causes.
- Dopamine agonists (cabergoline preferred over bromocriptine) are first-line treatment for prolactinomas.
- Always exclude pregnancy, hypothyroidism (TRH stimulates prolactin), and renal failure.
- Macroadenomas (>1 cm) can cause visual field defects (bitemporal hemianopia) by compressing the optic chiasm.
- Consider the hook effect with very high prolactin levels leading to falsely low immunoassay results; dilute sample if suspected.
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