Abstract
Seven healthy male volunteers aged 22-32 years were treated 4 times with 100 mg of
depot-testosterone in two days intervals (group I). Before the first and two days
after the last injection 100 µgm LRF were rapidly injected. Blood specimens were drawn
before and 30, 60, 90 and 120 min after the application of LRF. Four further subjects
(group II) were treated 4 times with 100 mg of testosterone in weekly intervals. LRF
was applied in the same way as in group I before treatment, 4 days after each injection
and 4 times after the last injection. LH and FSH determined by radioimmunoassay, testosterone
by a protein-binding-method.
In all 7 subjects of group I LH basal values after testosterone were suppressed whereas
the increase of LH after LRF was not influenced. There were, on the other hand, marked
differences in the FSH release between the subjects before testosterone treatment
as well as after treatment. In group II the maximal increase on LRF was reduced from
the 11th day onward with the lowest levels after 24 or 32 days. After the last application
of testosterone the peak values increased progressively. Again the reaction of FSH
after testosterone was different between the probands, depending on the initial values.
The plasma testosterone values exhibited a great intra- and interindividual variation.
There was no significant correlation between the testosterone plasma values and the
basal gonadotropin values or the degree of FSH or LH increase after LRF stimulation.
According to these results testosterone seems to block only the basal secretion of
LH when administered for a short time. With the same doses spread over a longer period
of time also the LRF induced LH release can be depressed. The negative feedback of
testosterone on FSH is more rapid and more pronounced than on LH. No convincing explanation
for the differences between LH and FSH in the pattern of reaction to LRF can yet be
given.
Key words
LH-Release - FSH-Release - LRF - Hypothalamus - Pituitary gland - Testosterone
