title: Seasonal variation in the secretion of mammotrophic hormones in normal women and women with previous breast cancer.
abstract: Hormones such as melatonin whose serum concentrations vary seasonally have been previously implicated in the growth of breast cancer. The present study was undertaken to identify possible seasonal variation in a range of mammotrophic hormones which could exert a chronobiologic influence in women with breast tumours. Fifteen premenopausal women with a history of previous breast cancer (BC subjects) and 10 control women underwent 2-hourly serum sampling for 24 h at both summer and winter solstice for measurement of melatonin, growth hormone (GH), insulin-like growth factor-I (IGF-I), cortisol, prolactin and thyrotrophin (TSH). Hormone secretion at the different seasons was compared by measuring the area under the 24 h serum hormone concentration x time curves and by time series analysis of summer-to-winter differences in hormone concentration. Control women had significantly higher GH and IGF-I levels in summer compared to winter and significantly higher cortisol secretion in winter than summer. In contrast, BC women had no significant seasonal difference in IGF-I concentrations and had a reversal of the normal seasonal pattern of melatonin secretion, although seasonal changes in GH production were similar to controls. Prolactin and TSH showed no significant summer/winter variation in either group. Thus, seasonal variations in hormone secretion seen in normal women were, with exception of GH, absent or reversed in women with a previous history of breast cancer. As a result these individuals may be exposed to an asynchronous hormonal stimulus which could influence tumour growth. These changes could reflect a constitutional abnormality in BC women or may have been induced by the previous breast tumour.
authors.affiliation: Department of Medicine, Auckland University School of Medicine, New Zealand.
authors.forename: I M
authors.initials: IM
authors.lastname: Holdaway
authors.forename: B H
authors.initials: BH
authors.lastname: Mason
authors.forename: E E
authors.initials: EE
authors.lastname: Gibbs
authors.forename: C
authors.initials: C
authors.lastname: Rajasoorya
authors.forename: A
authors.initials: A
authors.lastname: Lethaby
authors.forename: K D
authors.initials: KD
authors.lastname: Hopkins
authors.forename: M C
authors.initials: MC
authors.lastname: Evans
authors.forename: T
authors.initials: T
authors.lastname: Lim
authors.forename: B
authors.initials: B
authors.lastname: Schooler
mesh_terms: D001943:Breast Neoplasms / Q000503:physiopathology*; D005260:Female; D006728:Hormones / Q000378:metabolism*; D019382:Human Growth Hormone / Q000378:metabolism; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008550:Melatonin / Q000378:metabolism; D008875:Middle Aged; D017697:Premenopause; D011388:Prolactin / Q000378:metabolism; D012621:Seasons; D013972:Thyrotropin / Q000378:metabolism
chemical_list: D006728:Hormones; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D013972:Thyrotropin; D008550:Melatonin; D006854:Hydrocortisone