Differentials
Non-functioning pituitary macroadenomas
SIGNS / SYMPTOMS
May be no differentiating signs or symptoms.
INVESTIGATIONS
Usually mild hyperprolactinaemia up to 2000 mIU/L (100 micrograms/L) in the presence of a large pituitary mass compressing the pituitary stalk (disconnection hyperprolactinaemia).
Pituitary MRI imaging demonstrates a macroadenoma. The mild elevation in prolactin for a pituitary adenoma this size makes this diagnosis, rather than a prolactinoma, more likely.
Drug-induced hyperprolactinaemia
SIGNS / SYMPTOMS
There may be a drug history of antipsychotics, antidepressants, opiates, anti-emetics, oestrogens, H2 blockers, or verapamil.
INVESTIGATIONS
Prolactin evaluation after the patient stops the drug confirms decreasing prolactin levels. It may not be possible to discontinue certain medications, particularly antipsychotic medication. In this circumstance, pituitary MRI may help differentiate between drug-induced hyperprolactinaemia and elevated prolactin due to a sellar mass.[11]
Primary hypothyroidism
SIGNS / SYMPTOMS
There may be weight gain, cold intolerance, dry skin, constipation, or lethargy. In mild or subclinical hypothyroidism, there may be no differentiating symptoms.
INVESTIGATIONS
Thyroid function tests confirm primary hypothyroidism. Hyperprolactinaemia should normalise following thyroid hormone replacement.
Renal insufficiency
SIGNS / SYMPTOMS
May be no clear differentiating signs or symptoms.
INVESTIGATIONS
Prolactin evaluation after renal improvement.
Elevated serum creatinine, reduced creatinine clearance.
Pregnancy
SIGNS / SYMPTOMS
May be no initial differentiating signs or symptoms.
INVESTIGATIONS
Pregnancy test is positive.
Polycystic ovarian syndrome
SIGNS / SYMPTOMS
Hirsutism or acne may be present. Body mass index may be >25 kg/m². Menstrual irregularity may occur as with prolactinomas, but the history of oligo- or amenorrhoea is often longer in polycystic ovarian disease.
INVESTIGATIONS
Testosterone may be elevated. Sex hormone binding globulin may be low. Presence of ovarian cysts demonstrated on ultrasound.
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