Hormones and the Treatment of Sterility

Treating sterility with hormones is not always successful. Failure is due sometimes to the fact that the exact amounts of the various hormones necessary for normal reproduction are not known, and the use of hormones has of necessity been largely on a trial and error basis. Some conditions are benefited, however, by treatment with appropriate hormones.

In males that fail to produce sperm in normal amounts or in females that fail to come in heat, the use of pituitary hormones is helpful. Pregnant-mare serum has been commonly used for such conditions. Most cows will come in heat after a 1,500-unit dose, and many will conceive. Similar doses given at intervals to bulls often increase the production of sperm. The treatment seems to be most successful with younger bulls. It is very difficult to restore sperm production in aged bulls, and in most cases no responses are obtainable with any treatment now available. Stilbestrol also has been used often to bring cows in heat. It is rare to have cows so treated conceive at such artificially induced heat periods, but after heat has thus been brought on once, some will show heat at regular intervals without further treatment.

Pregnant-mare serum has been used widely in attempts to induce out-of-season estrus and ovulation in animals, such as sheep and goats, that normally do not breed in the spring and summer. Efforts in this direction have met with some success, and out-of-season pregnancies and normal births have resulted. Uniformly good results, however, have not been obtained, an indication that not all the factors involved are clearly understood. The successful discharge and fertilization of several eggs from the ovary, followed by multiple births, have occurred as a result of hormone treatment in cows, mares, and ewes.

Some females show regular heat periods, usually of reduced intensity, but still do not settle. Young females exhibit this behavior oftener than older females. These animals develop follicles and eggs, but the follicle fails to rupture and release the egg so that it may be fertilized. Treatment with stilbestrol or chorionic gonadotropin containing luteinizing hormone is useful in such cases, because LH is apparently not produced in sufficient quantity to cause ovulation. Stilbestrol, an estrogen, stimulates the pituitary to release LH. Both materials have given successful results in many instances. In one experiment conducted with cows, chorionic gonadotropin was effective in 50 percent of the cases. Successful use of these hormones will depend on proper timing of the dose. A mature follicle—one that is ready to rupture must be present at time of treatment and the hormones, therefore, should be given 2 to 3 days before the heat period is due.

Nymphomania, or constant heat, is another condition that is associated with sterility in many females. Multiple follicles or cysts of large size appear on the ovaries and produce sufficient estrogen to cause constant estrus. Even though these animals may be bred daily, they fail to conceive. The defect seems to be that there is too much follicle-stimulating hormone and too little luteinizing hormone. Workers at the Wisconsin Agricultural Research Station have found that, by injecting small amounts of a crude pituitary preparation into the blood of cows, they can correct the troublesome condition in a high proportion of cases. Research at the University of Pennsylvania has shown that similar good results can be obtained by injecting large doses of chorionic gonadotropin into the muscles. Our own results with a few cases are encouraging.

Lack of sexual desire in the male is often a troublesome condition in animals that are otherwise completely fertile. Two materials have been used in efforts to overcome the condition. The male sex hormone, testosterone, is often of definite benefit in such cases. The feeding of substances containing thyroxine may also be helpful.

The use of the hormones we have mentioned seldom brings lasting results. Often the treatment has to be repeated. One may well question the desirability of perpetuating such abnormal animals, as their offspring might suffer similar defects. But with certain valuable individuals and in emergencies where maximum livestock production is wanted, this kind of treatment may have its uses.

Both female sex hormones, estrogen and progesterone, influence the growth of the udder. Estrogen is responsible for the development of the tubular structures, the ducts and cisterns of the udder. These tubes branch out from the teat canal and hold the milk as it is secreted into the udder. Progesterone causes the development of the cells within the udder that actually secrete milk, and is not concerned with tubular development.

Little, if any, of the two hormones is produced until sexual maturity is reached, that is, until heat periods appear; no decided udder growth occurs until that time. After puberty, the female sex hormones are produced in greater quantity and there is a gradual growth of the udder until the first pregnancy occurs. During pregnancy, estrogen and progesterone are secreted in still larger amounts. Udder growth, therefore, proceeds much more rapidly and by mid-pregnancy all the structures that are destined to function in the first lactation are probably present. The apparent growth of the udder that occurs from this time on is apparently largely due to enlargement of cells already present and to accumulations of secretions.

Secretions from the pituitary gland also participate in the growth of the mammary gland. If the pituitary gland is removed from experimental animals, estrogen and progesterone produce very little mammary gland growth. However, if extracts of the anterior pituitary gland or if pure anterior pituitary hormones are given together with estrogen and progesterone to such animals, essentially normal growth is obtained. The anterior pituitary hormones that have been shown to be involved in mammary-gland growth include prolactin, the adrenal-stimulating hormone and possibly the thyroid-stimulating and growth hormones. Whether there are additional specific mammary-stimulating hormones (mammogens) produced by the pituitary gland is a disputed question.