August 22, 2002
Genetics and Heredity
Question from Australia:
My partner is 30 years old, and his mother and mother’s father both have type 2 diabetes. His grandfather was approximately 52 years old and his mother was diagnosed at 46 years of age (having been tested since she was 30 years old). At the time of diagnosis, his mother was generally not excessively overweight. I am not sure about his grandfather. His mother and grandfather are quite tall and slim and carry most of their weight around their abdomen (apple tree figure).
My husband has a 25 year old brother and a 31 year old sister who had gestational diabetes during her first two pregnancies. (She has four children.) She also suffers from Graves’ Disease and has suffered approximately three occasions of hyperthyroidism since about the age of 26. I believe that two of the three occasions were linked to her last two pregnancies, as the hyperthyroidism reactivated not long after these births.
The only commonly obvious symptom that all siblings share is the occasional tendency to get overweight, which they all carry around their abdomen. My understanding is that while they all have hereditary risks of developing type 2, other risks are based on age, being overweight, inactivity and diet. Their sister’s conditions also suggest links with diabetes.
Their mother suggested a theory that the brothers are at greater risk of developing type 2 than their sister. The theory suggests that — as in this case — diabetes is passed through the generations from father to daughter, to grandson to great-granddaughter. In other words, it passes through the generations alternating from gender each generation (male to female to male to female, etc). Another sub theory is that as my partner is the first born male, he is at higher risk than his brother.
None of my research supports either of these theories. However, as my partner and I are planning to start a family, we want to ascertain the risks for both my partner developing diabetes, and — based on this theory — if we had a daughter the risks of her developing diabetes.
Answer:
I do not believe there is any science to back up these proposed theories. The genetic predisposition can go from either parent to a child of either gender.
My suggestion to you for your partner is to live a healthy lifestyle. Work hard to keep the weight off and exercise frequently. Even in families where there is a genetic predisposition, it may not come to pass because of the favorable lifestyle. He needs to be tested regularly by his doctor for the presence of diabetes. There is now even evidence that diabetes can be prevented through lifestyle and medication.
The reason a woman with gestational diabetes is at such risk for diabetes later on is that the pregnancy provides appropriate stress to induce insulin resistance. Those at risk cannot compensate and are at very high risk for developing diabetes later on.
JTL
