The Effect of Temperature Changes on the Thyroid-pituitary Relationship in Teleosts

An increase in the thyroid activity of teleosts correlated with an increase in environmental temperature has been recorded by Blanc & Buser (1949), Fortune (1953, 1955), and Barrington & Matty (1954); this has not been confirmed by Delsol & Flatin (1956) who found no effect, or by Olivereau (1950,1954, 1955 a, b, c) who demonstrated that increased temperature tended rather to decrease thyroid activity. The action of the thyrotrophic hormone (TSH) is intensified with increasing temperature (Olivereau, 1955 c; Delsol & Flatin, 1956). This is confirmed below. Such an action would be expected to lead to a consequent increase in thyroid hormone (TH) production with increased temperature, unless a compensatory decrease in TSH production takes place. Apart from seasonal changes (e.g. Fontaine, 1953; Olivereau, 1954) no information is available on the effect of temperature on the cells of the teleostean anterior pituitary which secrete thyrotrophic hormone (thyrotrophs). The experiments described here were designed to investigate this aspect and to extend previous observations on the effect of temperature on thyroid activity.