Absent and Infrequent Periods: Investigations

A minimal set of hormone investigations is likely to include FSH, LH, prolactin levels and thyroid function tests (Q6.8).Luteinising hormone (LH) levels rise just before ovulation (Q 2. 14;Figure 2. 3) and a high level with normal FSH should be assessed according to whether a spontaneous period occurs two weeks later (LH Surge Figure 2.3). Otherwise a high LH may suggest polycystic ovary syndrome (Q7.2). When both LH and FSH are elevated (hypergonadotrophic hypogonadism), the menopause should be suspected (Q 26.1). Occasionally, in younger women with amenorrhoea and hypogonadotrophic hypogonadism (Low gonadotrophin levels resulting in reduced ovarian hormone output), pregnancy or resumption of periods can occur and the diagnosis is resistant ovary syndrome. In these circumstances it seems as if there were no eggs timed for release during the episode of amenorrhoea (Q 2.3).

Low levels of gonadotrophins will result in low oestrogen levels and amenorrhoea (hypogonadotrophic hypogonadism). This may be seen in weight associated amenorrhoea (

Q6.8).

Kallman's syndrome is a combination of hypogonadotrophic hypogonadism and colour blindness.

An ultrasound examination of the pelvis has become virtually routine.

Oestradiol, SHBG and testosterone levels are often also helpful.

A progestogen challenge test provides some evaluation of oestrogen production. Dydrogesterone (Duphaston) or medroxyprogesterone acetate (Provera) are taken for five days. A withdrawal bleed between 2 and 5 days later is normal and regarded as a 'positive' result. A positive progestogen challenge test indicates that oestrogen levels have been enough to cause sufficient thickening of the lining of your womb for shedding to occur. A negative progestogen challenge test (assuming pregnancy has been excluded) indicates low oestrogen levels. Blood oestrogen levels fluctuate so that laboratory estimations are of limited value.

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