Dysmenorrhoea and PMDD — structured oral station (12 minutes)

Opening prompt — "How do you classify this 16-year-old's dysmenorrhoea, and what is its mechanism?"

Model response — primary dysmenorrhoea and the prostaglandin pathway: ^[1][2]

• "This is primary dysmenorrhoea: cramping lower abdominal pain in the absence of pelvic pathology, beginning within 6-12 months of menarche, peaking in the first 24-72 hours, with a normal pelvic examination."
• "The mechanism is prostaglandin-mediated. Late-luteal progesterone withdrawal triggers endometrial arachidonic acid release; cyclo-oxygenase converts it to PGF2alpha and PGE2; PGF2alpha causes myometrial contraction and spiral-arteriole vasoconstriction, producing uterine ischaemia and pain. NSAIDs block COX."^[1]

Probe 1 — "Walk me through your stepped management."

• "Step 1: an NSAID commenced at onset of menstruation — ibuprofen 400 mg three times daily with food, or naproxen 500 mg then 250 mg every 6-8 hours — plus topical heat and exercise. The Cochrane review confirms NSAIDs are more effective than placebo." ^[1]
• "Step 2: a combined oral contraceptive or a progestin to suppress ovulation and thin the endometrium." ^[2]
• "Step 3: a levonorgestrel intrauterine system for refractory primary dysmenorrhoea."
• "Step 4: investigate for a secondary cause if there is no response at 3-6 months — ACOG Committee Opinion 760."^[2]

Probe 2 — "The 30-year-old with severe premenstrual mood symptoms — what are her DSM-5 PMDD criteria?"

• "Criterion A: at least five symptoms in the final week before menses, improving within a few days of onset and minimal or absent in the week postmenses." ^[3]
• "Criterion B (one or more required): marked affective lability; marked irritability or anger; marked depressed mood; marked anxiety or tension." ^[3]
• "Criterion C: additional symptoms (decreased interest, concentration difficulty, lethargy, appetite change, sleep change, feeling overwhelmed, physical symptoms) bring the total to five." ^[3]
• "Criterion F: confirmed by prospective daily ratings over at least two symptomatic cycles — and there must be a symptom-free follicular phase."^[3]

Probe 3 — "Her symptom diary shows symptoms throughout the cycle. What does that mean?"

• "It is not PMDD — DSM-5 Criterion E requires that the disturbance is not merely an exacerbation of another psychiatric disorder. Persistent symptoms throughout the cycle point to a primary mood disorder (depression, dysthymia, generalised anxiety), and I would arrange formal psychiatric assessment before prescribing an SSRI — particularly to exclude bipolar disorder, where SSRIs can destabilise mood."^[3]

Probe 4 — Communication: "She asks whether she needs to take an antidepressant every day."

• "I would say: 'For PMDD, an SSRI works whether you take it every day or only in the two weeks before your period — the luteal phase. The Cochrane review confirms both are effective. We will choose the option that fits your life and your symptoms.' That gives her the evidence and the choice."^[4]