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Iodine intake and the seasonal incidence of thyrotoxicosis in New Zealand
Author(s) -
Ford H. C.,
Johnson L. A.,
Feek C. M.,
Newton J. D.
Publication year - 1991
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.1991.tb00290.x
Subject(s) - endocrinology , medicine , incidence (geometry) , biology , optics , physics
Summary We explored a possible relationship between the seasonal variation In the Incidence of thyrotoxicosis In our area and Iodine Intake, as assessed by measuring the 24‐h urinary iodide excretion rate eight times at 3‐month Intervals in a group of normal subjects and in 992 outpatient specimens over a 2‐year period (1988–1990). For the period 1978–1990, 139 cases of thyrotoxicosis were diagnosed during the warmer half of the year (November‐April) and 100 cases during the cooler half (May‐October). This difference was statistically highly significant (P = 0·013). A similar disproportionality in the incidence of thyrotoxicosis was observed between the warmer (57%) and cooler (43%) halves of the year for the period 1988–1990. During the 1988–1990 period there was no discernible seasonal variation In either the milk iodide concentration or In the cumulative mean 24‐h urinary iodide excretion rates for the normal subjects or the outpatients. We conclude that the higher proportion of thyrotoxic patients diagnosed during the warmer 6‐month period of the year In our area is best explained by the fact that symptoms tend to be less tolerable in warm weather. A comparison of our findings on 24‐h urinary Iodide excretion rates with data collected in our area 25 years ago suggested that Iodine Intake may have declined