A 24-year-old woman presents with the absence of periods for 9 months.... Case Study

A 24-year-old woman presents with the absence of periods for 9 months. She started her periods at the age of 13 years and had a regular 28-day cycle until 18 months ago. The periods then became irregular, occurring every 2–3 months until they stopped completely.
She has also had headaches for the last few months and is not sure if this is related. She has a regular sexual partner and uses condoms for contraception. She has never been pregnant. There is no previous medical history of note.
She works as a primary school teacher and drinks approximately 4 units of alcohol per week. She does not smoke or use recreational drugs. She jogs and swims in her spare time.
Examination
The woman is of average build. The blood pressure and general observations are normal.
The abdomen is soft and non-tender and speculum and bimanual examination are unremarkable.

Investigations: 
Follicle-stimulating hormone  = 7 IU/L (normal on day 2-5 = 1–11 IU/L)
Luteinizing hormone  = 4 IU/L (normal on day 2-5 = 0.5–14.5 IU/L)
Prolactin   = 1800 mu/L (normal range = 90–520 mu/L)
Testosterone  = 1.8 nmol/L (normal range = 0.8–3.1 nmol/L)

A MRI scan of the head was done which revealed asymmetrical enlargement of pituitary gland,
representative of a small pituitary adenoma most likely a prolactinoma.

Case Discussion:

The investigations show a high-prolactin and a space-occupying lesion in the pituitar fossa in the region of the anterior pituitary. This is consistent with a pituitary adenoma (prolactinoma).
Prolactin should always be measured in a woman with amenorrhoea. Care should be taken in interpreting the results, as levels up to 1000 mu/L can be found as a result of stress (even due to venepuncture), breast examination or in association with polycystic ovarian syndrome).
Above 1000 mu/L the usual cause is a pituitary adenoma (micro- or macroscopic).

Differential diagnosis of secondary amenorrhoea
Hypothalamic causes:
• chronic illness
• anorexia
• excessive exercise
• stress
Pituitary causes:
• hyperprolactinaemia (e.g. drugs, tumor)
• hypothyroidism
• breast-feeding
Ovarian causes:
• polycystic ovarian syndrome
• premature ovarian failure
• iatrogenic (chemotherapy, radiotherapy, oophorectomy)
• long-acting progesterone contraception
Uterine causes:
• pregnancy
• Asherman’s syndrome
• cervical stenosis

Further investigation
Visual fields should be checked, as visual field defects may be present with a large tumor.
The other important investigation in any woman with amenorrhoea is a pregnancy test, although with this history this would be very unlikely. (Prolactin is also raised in pregnancy.)

Management

• Most prolactinomas respond to medical treatment with bromocriptine or cabergoline.
• Maintaining the prolactin level below 1000 mu/L causes menstruation (and ovulation) to return in most women. This can be continued indefinitely or until pregnancy is achieved if the presenting complaint is of infertility.

Key Learning Points in this case: 

• Hyperprolactinaemia is a common cause of secondary amenorrhoea.

• Prolactin levels up to 1000 u/L may be due to non-pathological causes such as stress.

• Prolactinomas can usually be treated with medical suppression, and surgery is only indicated rarely.