title: Sex hormone concentrations in blood serum from the north Atlantic fin whale (Balaenoptera physalus).
abstract: Blood serum concentrations of testosterone and progesterone were measured in postmortem samples taken at sea from 814 fin whales (Balaenoptera physalus) caught during the summers (June-September) of 1981-1989. The ages of 781 of these animals were also assessed. The testosterone concentrations in samples from 352 males averaged 2 nmol/l; 41 samples had concentrations of 0.1 nmol/l or lower and 34 of these came from whales aged between 2 and 14 years and showed a Gaussian type of age distribution with a peak number at 7 to 8 years. The mean testosterone concentrations in the males increased by more than fourfold between June and August. Serum progesterone concentrations of the 462 females fell into three separate groups: (1) group I with values < or = 0.1 nmol/l; (2) group II with intermediate values of > 0.1 nmol/l but < 10 nmol/l; (3) group III with values of > or = 10 nmol/l. These three groups of females seemed to consist respectively of young sexually immature females, mature non-pregnant females and pregnant females. The age distribution in the groups indicated that puberty in females is attained chiefly between the ages of 7 and 10. The yearly pregnancy rate (that percentage of all females caught and studied in a year which had progesterone values > or = 10 nmol/l) was between 35% and 55%, except in 1987 when it was 67%. The yearly pregnancy rate would range from 56% to 93% if only mature females (i.e. those with serum progesterone > 0.1 nmol/l) were considered.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: University Hospital, Department of Clinical Chemistry, Reykjavík, Iceland.
authors.forename: J M
authors.initials: JM
authors.lastname: Kjeld
authors.forename: J
authors.initials: J
authors.lastname: Sigurjónsson
authors.forename: A
authors.initials: A
authors.lastname: Arnason
mesh_terms: D000818:Animals; D004958:Estradiol / Q000097:blood; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood*; D008297:Male; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood*; D011374:Progesterone / Q000097:blood; D011863:Radioimmunoassay; D012741:Sexual Maturation / Q000502:physiology; D013739:Testosterone / Q000097:blood; D014907:Whales / Q000097:blood*
chemical_list: D012739:Gonadal Steroid Hormones; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol