Hypothalamic causes of secondary amenorrhoea

Hypothalamic causes of amenorrhoea may be either primary or secondary. Primary hypothalamic lesions include craniopharyngiomas, germinomas, gliomas and dermoid cysts. These hypothalamic lesions either disrupt the normal pathway of prolactin inhibitory factor (dopamine), thus causing hyperprolactinaemia or compress or destroy hypothalamic and pituitary tissue. Treatment is usually surgical, with additional radiotherapy if required. Hormone replacement therapy is required to mimic ovarian function, and if the pituitary gland is damaged either by the lesion or by the treatment, replacement thyroid and adrenal hormones are required.

Secondary hypogonadotrophic hypogonadism may result from systemic conditions including sarcoidosis, tuberculosis as well as following head injury or cranial irradiation. Sheehan's syndrome, the result of profound and prolonged hypotension on the sensitive pituitary gland, enlarged by pregnancy, may also be a cause of hypogonadotrophic hypogonadism in someone with a history of a major obstetric haemorrhage [40]. It is essential to assess the pituitary function fully in all these patients and then instigate the appropriate replacement therapy. Ovulation may be induced with pulsatile subcutaneous GnRH or human menopausal gonadotropins (hMG). The administration of pulsatile GnRH provides the most 'physiological' correction of infertility caused by hypogonadotrophic hypogonadism and will result in unifollicular ovulation, while hMG therapy requires close monitoring to prevent multiple pregnancy. Purified or recombinant FSH preparations are not suitable for women with hypogonadotrophic hypogonadism (or pituitary hypogonadism) as these patients have absent endogenous production of LH and so while follicular growth may occur, oestrogen biosynthesis is impaired [41]. Thus hMG, which contains FSH and LH activity, is necessary for these patients.



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