Human mitochondrial DNA polymerase, encoded by POLG, contains a polyglutamine tract encoded by a CAG microsatellite repeat. Analysis of POLG genotypes in different populations identified an association between absence of the common, ten-repeat allele and male infertility typified by a range of sperm quality defects but excluding azoospermia.

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Detailed medical and clinical examinations were carried out on 1608 men attending an infertility clinic to determine if any of those exhibiting abnormal semenograms also had any other readily identifiable clinical condition. In all, 1210 men showed abnormal semenograms according to World Health Organization criteria. Karyotyping of the white blood cells in these 1210 men revealed 44 (3.6%) individuals with either autosomal or sex chromosomal aberrations. However, no single characteristic feature of their semenogram or clinical condition was of any diagnostic value to predict the existence of a chromosomal anomaly.

Serum prolactin and gonadotrophin concentrations were measured by radioimmunoassay in 106 women with amenorrhoea. Prolactin was normal in those with weight related disorders, primary ovarian failure, those with a variety of systemic diseases and in those in whom amenorrhoea followed treatment with the oral contraceptive and in unexplained primary amenorrhoea. Gonadotrophin concentrations in the above patients were normal except in those with primary ovarian failure. Prolactin was elevated in eight of forty patients (20%) with functional secondary amenorrhoea and was greatly raised in all but one of the thirteen women in this series with pituitary tumours (five of whom were studied only after treatment). Only three patients in each of the last two groups had galactorrhoea. Gonadotrophin levels were normal or slightly raised in all of the hyperprolactinaemic patients apart from those studied after hypophysectomy. Four hyperprolactinaemic patients (three with pituitary tumours and one with functional amenorrhoea) who did not have galactorrhoea have been treated with bromocriptine. Prolactin secretion was reduced in all patients and, in the two with normal gonadotrophins, ovulatory menstruation was resumed. One became pregnant in the second ovulation cycle after starting treatment. We conclude that, despite the rarity of galactorrhoea, hyperprolactinaemia is common in patients with functional amenorrhoea and in those with pituitary tumours. Treatment with bromocriptine in patients with normal gonadotrophins restores ovulation when the infertility is due to prolactin excess.