Multiple Endocrine Gland Hypoplasia in Lambs: Thyroid, Adrenal & Pituitary Disorders

Multiple endocrine gland hypoplasia in lambs is a congenital developmental disorder. That means the lamb is born with one or more hormone-producing glands that did not form normally before birth. In reported sheep cases, the glands most often involved are the pituitary and adrenal glands, and some lambs also show thyroid atrophy or hypoplasia. These glands help regulate growth, metabolism, stress response, and the normal hormonal signals that support birth and early survival.

Because these hormones are so important, affected lambs may be born weak, poorly developed, or nonviable. Some pregnancies are also unusually long because the fetal pituitary-adrenal system helps trigger normal parturition. When that system fails, the ewe may not lamb on time, and dystocia or delivery of an oversized, postmature, or dead lamb can follow.

This condition is considered rare, but it matters because it can cause major lamb losses and may look similar to other neonatal problems such as iodine deficiency, congenital goiter, infectious fetal disease, or severe prematurity. A careful workup with your vet is important so the flock problem is not mistaken for a simple nutrition issue.

In practical terms, this is usually a flock health and breeding management problem as much as an individual lamb problem. If more than one related lamb is affected, your vet may discuss inherited defects, toxic plant exposure during pregnancy, or other causes of fetal endocrine damage.

The underlying cause is abnormal fetal development of endocrine tissue. In large-animal medicine, pituitary and adrenal hypoplasia are well recognized causes of prolonged gestation, and Merck notes that combined pituitary and adrenal abnormalities can occur as inherited developmental defects. In sheep, prolonged gestation has also been reported when affected lambs show atrophy of the pituitary, adrenal, and thyroid glands.

Possible causes include inherited recessive defects, toxic plant exposure during pregnancy, and fetal infections or brain malformations that damage pituitary function. Merck specifically describes prolonged gestation in sheep associated with maternal ingestion of Salsola tuberculatiformis, where affected lambs had pituitary, adrenal, and thyroid atrophy. Border disease virus and other fetal infections can also interfere with brain development, and pituitary compromise may follow.

It is also important to separate this disorder from nutritional iodine deficiency and congenital goiter, which are more common in lambs than true multigland hypoplasia. Iodine deficiency in pregnant ewes can produce weak or stillborn lambs, sometimes with enlarged thyroid glands and sometimes without obvious neck swelling. Goitrogenic feeds such as some brassicas can worsen that risk.

Because several different problems can produce similar signs, your vet will usually consider the whole picture: breeding history, related animals affected, gestation length, pasture and feed exposures, mineral program, and necropsy findings if a lamb dies.

Diagnosis starts with a full history and flock pattern review. Your vet will want to know whether the pregnancy was prolonged, whether dystocia occurred, whether affected lambs are related, what the ewe ate during gestation, and whether there have been other stillbirths, weak lambs, or congenital defects in the flock.

In a live lamb, your vet may perform a physical exam, temperature check, glucose assessment, and basic bloodwork if practical. Depending on the case, testing may include thyroid hormone measurements, electrolyte and metabolic screening, and evaluation for infectious or nutritional causes. These tests can support endocrine dysfunction, but they may not fully define which glands are abnormal in a field setting.

A necropsy is often the most useful diagnostic step when a lamb dies or is nonviable. Gross examination and histopathology can identify hypoplasia or atrophy of the pituitary, adrenal, and thyroid glands and help rule out congenital infection, trauma, or other birth defects. For flock-level decision making, this is often more informative than treating future cases blindly.

Your vet may also recommend checking the ewe flock's iodine and overall mineral program, reviewing forage sources for goitrogens, and considering breeding records if an inherited defect is suspected. That broader approach helps prevent repeated losses and supports more accurate breeding and nutrition decisions.

Prevention depends on the cause, so the first step is getting the most accurate diagnosis possible. If a lamb dies, a necropsy can be one of the most cost-effective tools for protecting the rest of the flock. Without that information, inherited defects, toxic exposures, and nutritional thyroid disease can look very similar.

Work with your vet to review the flock's breeding records and family patterns. If related lambs are repeatedly affected, an inherited defect becomes more likely, and your vet may recommend avoiding repeat matings or culling from the breeding program. This is especially important in small flocks where the same sire lines are used heavily.

Nutrition also matters. Merck notes that iodine-deficiency goiter is most common in neonatal lambs in iodine-deficient areas, and Cornell and other sheep health resources emphasize that pregnant ewes need a reliable sheep-specific mineral program. Goitrogenic feeds, including some brassicas, can increase risk in offspring if fed for prolonged periods during gestation. Your vet can help you decide whether forage testing, ration review, or targeted supplementation makes sense for your area.

Finally, reduce preventable fetal stress by maintaining good ewe health, vaccination planning, parasite control, and pregnancy nutrition. Those steps will not prevent every congenital defect, but they do lower the chance that infectious disease, poor fetal development, or mineral imbalance will be mistaken for a rare endocrine disorder.