Effects of elevated gonadotropin levels on thyroid function in the male rat.
In order to determine if thyroid disease in hypogonadal men is the result of chronic elevation of serum gonadotropins, thyroid histology and serum thyroid hormone levels were evaluated in male rats that had been castrated either 2 weeks or 15 months previously. Despite significantly elevating serum LH levels, castration did not affect thyroid structure or function. Serum total T4 levels were reduced with age in both short and long-term castrate animals but returned to the levels seen in young rats when testosterone was replaced. Testosterone replacement also increased free T4 levels in both the young and old castrate rats. Neither age nor testosterone replacement affected serum T3 or TSH levels.
Steger
R W
RW
Department of Physiology, Southern Illinois University School of Medicine, Carbondale 62901-6512.
Chandrashekar
V
V
Bartke
A
A
Wortsman
J
J
Newton
S C
SC
Smallridge
R C
RC
Dietrich
J
J
D000818:Animals; D006062:Gonadotropins / Q000097:blood*; D007006:Hypogonadism / Q000150:complications*; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D009919:Orchiectomy; D051381:Rats; D011916:Rats, Inbred F344; D013739:Testosterone / Q000008:administration & dosage; D013959:Thyroid Diseases / Q000209:etiology*; D013961:Thyroid Gland / Q000473:pathology / Q000503:physiopathology*; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D006062:Gonadotropins; D013963:Thyroid Hormones; D014284:Triiodothyronine; D013739:Testosterone; D007986:Luteinizing Hormone; D013972:Thyrotropin; D013974:Thyroxine